Remove suppressions for ShouldNotSubclass.

We have disabled the check for our packages internally:

- Often it fires because we're implementing `Future`. It's very true that "normal" code shouldn't implement `Future`, but _someone_ needs to, and that someone is us.
- Sometimes it fires because we're extending a type like `AtomicReference` to shave off an object and some indirection. I won't claim to have data that shows that this is actually justified, but for better or for worse, it's a conscious decision that we're making.
- I also see at least two suppressions for extending `Throwable`. There's probably no compelling reason for this, but we don't actually throw them, and changing them now would carry at least some risk.

Of course, it's possible that `ShouldNotSubclass` would eventually have caught new occurrences that we _would_ have cared about. But historically that doesn't seem to have been the case.

RELNOTES=n/a
PiperOrigin-RevId: 375982730

android/guava/src/com/google/common/util/concurrent/AbstractFuture.java

@@ -65,7 +65,7 @@
  * @since 1.0
  */
 // we use non-short circuiting comparisons intentionally
-@SuppressWarnings({"ShortCircuitBoolean", "ShouldNotSubclass"})
+@SuppressWarnings("ShortCircuitBoolean")
 @GwtCompatible(emulated = true)
 @ReflectionSupport(value = ReflectionSupport.Level.FULL)
 public abstract class AbstractFuture<V> extends InternalFutureFailureAccess

android/guava/src/com/google/common/util/concurrent/ExecutionSequencer.java

@@ -284,7 +284,6 @@ enum RunningState {
    * properties; for example, calling WeakReference.get() on Android will block during an
    * otherwise-concurrent GC cycle.
    */
-  @SuppressWarnings("ShouldNotSubclass") // Saving an allocation here is worth it
   private static final class TaskNonReentrantExecutor extends AtomicReference<RunningState>
       implements Executor, Runnable {
 

android/guava/src/com/google/common/util/concurrent/ForwardingFuture.java

@@ -36,7 +36,6 @@
  */
 @CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
 @GwtCompatible
-@SuppressWarnings("ShouldNotSubclass")
 @ElementTypesAreNonnullByDefault
 public abstract class ForwardingFuture<V extends @Nullable Object> extends ForwardingObject
     implements Future<V> {

android/guava/src/com/google/common/util/concurrent/ForwardingListenableFuture.java

@@ -30,7 +30,6 @@
  * @author Shardul Deo
  * @since 4.0
  */
-@SuppressWarnings("ShouldNotSubclass")
 @CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
 @GwtCompatible
 @ElementTypesAreNonnullByDefault

android/guava/src/com/google/common/util/concurrent/Futures.java

@@ -470,7 +470,6 @@ public static <I, O> ListenableFuture<O> transform(
    */
   @Beta
   @GwtIncompatible // TODO
-  @SuppressWarnings("ShouldNotSubclass")
   public static <I, O> Future<O> lazyTransform(
       final Future<I> input, final Function<? super I, ? extends O> function) {
     checkNotNull(input);

android/guava/src/com/google/common/util/concurrent/ImmediateFuture.java

@@ -29,7 +29,6 @@
 @GwtCompatible
 @ElementTypesAreNonnullByDefault
 // TODO(cpovirk): Make this final (but that may break Mockito spy calls).
-@SuppressWarnings("ShouldNotSubclass")
 class ImmediateFuture<V extends @Nullable Object> implements ListenableFuture<V> {
   static final ListenableFuture<?> NULL = new ImmediateFuture<@Nullable Object>(null);
 

android/guava/src/com/google/common/util/concurrent/InterruptibleTask.java

@@ -24,7 +24,6 @@
 import java.util.concurrent.locks.LockSupport;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
-@SuppressWarnings("ShouldNotSubclass")
 @GwtCompatible(emulated = true)
 @ReflectionSupport(value = ReflectionSupport.Level.FULL)
 @ElementTypesAreNonnullByDefault

android/guava/src/com/google/common/util/concurrent/JdkFutureAdapters.java

@@ -97,7 +97,6 @@ public final class JdkFutureAdapters {
    * <p>If the delegate future is interrupted or throws an unexpected unchecked exception, the
    * listeners will not be invoked.
    */
-  @SuppressWarnings("ShouldNotSubclass")
   private static class ListenableFutureAdapter<V extends @Nullable Object>
       extends ForwardingFuture<V> implements ListenableFuture<V> {
 

android/guava/src/com/google/common/util/concurrent/ListenableFuture.java

@@ -115,7 +115,6 @@
  * that affects users, especially users of the Android Gradle Plugin, since the plugin developers
  * put in a special hack for us: https://issuetracker.google.com/issues/131431257)
  */
-@SuppressWarnings("ShouldNotSubclass")
 @DoNotMock("Use the methods in Futures (like immediateFuture) or SettableFuture")
 /*
  * It would make sense to also annotate this class with @ElementTypesAreNonnullByDefault. However,

android/guava/src/com/google/common/util/concurrent/ListenableFutureTask.java

@@ -40,7 +40,6 @@
  * @author Sven Mawson
  * @since 1.0
  */
-@SuppressWarnings("ShouldNotSubclass")
 @GwtIncompatible
 @ElementTypesAreNonnullByDefault
 public class ListenableFutureTask<V extends @Nullable Object> extends FutureTask<V>

android/guava/src/com/google/common/util/concurrent/ListenableScheduledFuture.java

@@ -27,7 +27,6 @@
  */
 @Beta
 @GwtCompatible
-@SuppressWarnings("ShouldNotSubclass")
 @ElementTypesAreNonnullByDefault
 public interface ListenableScheduledFuture<V extends @Nullable Object>
     extends ScheduledFuture<V>, ListenableFuture<V> {}

android/guava/src/com/google/common/util/concurrent/ServiceManager.java

@@ -823,6 +823,5 @@ protected void doStop() {
   }
 
   /** This is never thrown but only used for logging. */
-  @SuppressWarnings("ShouldNotSubclass")
   private static final class EmptyServiceManagerWarning extends Throwable {}
 }

futures/listenablefuture1/src/com/google/common/util/concurrent/ListenableFuture.java

@@ -115,7 +115,6 @@
  * that affects users, especially users of the Android Gradle Plugin, since the plugin developers
  * put in a special hack for us: https://issuetracker.google.com/issues/131431257)
  */
-@SuppressWarnings("ShouldNotSubclass")
 @DoNotMock("Use the methods in Futures (like immediateFuture) or SettableFuture")
 /*
  * It would make sense to also annotate this class with @ElementTypesAreNonnullByDefault. However,

guava/src/com/google/common/util/concurrent/AbstractFuture.java

@@ -65,7 +65,7 @@
  * @since 1.0
  */
 // we use non-short circuiting comparisons intentionally
-@SuppressWarnings({"ShortCircuitBoolean", "ShouldNotSubclass"})
+@SuppressWarnings("ShortCircuitBoolean")
 @GwtCompatible(emulated = true)
 @ReflectionSupport(value = ReflectionSupport.Level.FULL)
 public abstract class AbstractFuture<V> extends InternalFutureFailureAccess

guava/src/com/google/common/util/concurrent/ExecutionSequencer.java

@@ -284,7 +284,6 @@ enum RunningState {
    * properties; for example, calling WeakReference.get() on Android will block during an
    * otherwise-concurrent GC cycle.
    */
-  @SuppressWarnings("ShouldNotSubclass") // Saving an allocation here is worth it
   private static final class TaskNonReentrantExecutor extends AtomicReference<RunningState>
       implements Executor, Runnable {
 

guava/src/com/google/common/util/concurrent/ForwardingFuture.java

@@ -36,7 +36,6 @@
  */
 @CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
 @GwtCompatible
-@SuppressWarnings("ShouldNotSubclass")
 @ElementTypesAreNonnullByDefault
 public abstract class ForwardingFuture<V extends @Nullable Object> extends ForwardingObject
     implements Future<V> {

guava/src/com/google/common/util/concurrent/ForwardingListenableFuture.java

@@ -30,7 +30,6 @@
  * @author Shardul Deo
  * @since 4.0
  */
-@SuppressWarnings("ShouldNotSubclass")
 @CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
 @GwtCompatible
 @ElementTypesAreNonnullByDefault

guava/src/com/google/common/util/concurrent/Futures.java

@@ -503,7 +503,6 @@ public static <I, O> ListenableFuture<O> transform(
    */
   @Beta
   @GwtIncompatible // TODO
-  @SuppressWarnings("ShouldNotSubclass")
   public static <I, O> Future<O> lazyTransform(
       final Future<I> input, final Function<? super I, ? extends O> function) {
     checkNotNull(input);

guava/src/com/google/common/util/concurrent/ImmediateFuture.java

@@ -29,7 +29,6 @@
 @GwtCompatible
 @ElementTypesAreNonnullByDefault
 // TODO(cpovirk): Make this final (but that may break Mockito spy calls).
-@SuppressWarnings("ShouldNotSubclass")
 class ImmediateFuture<V extends @Nullable Object> implements ListenableFuture<V> {
   static final ListenableFuture<?> NULL = new ImmediateFuture<@Nullable Object>(null);
 

guava/src/com/google/common/util/concurrent/InterruptibleTask.java

@@ -24,7 +24,6 @@
 import java.util.concurrent.locks.LockSupport;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
-@SuppressWarnings("ShouldNotSubclass")
 @GwtCompatible(emulated = true)
 @ReflectionSupport(value = ReflectionSupport.Level.FULL)
 @ElementTypesAreNonnullByDefault

guava/src/com/google/common/util/concurrent/JdkFutureAdapters.java

@@ -97,7 +97,6 @@ public final class JdkFutureAdapters {
    * <p>If the delegate future is interrupted or throws an unexpected unchecked exception, the
    * listeners will not be invoked.
    */
-  @SuppressWarnings("ShouldNotSubclass")
   private static class ListenableFutureAdapter<V extends @Nullable Object>
       extends ForwardingFuture<V> implements ListenableFuture<V> {
 

guava/src/com/google/common/util/concurrent/ListenableFuture.java

@@ -115,7 +115,6 @@
  * that affects users, especially users of the Android Gradle Plugin, since the plugin developers
  * put in a special hack for us: https://issuetracker.google.com/issues/131431257)
  */
-@SuppressWarnings("ShouldNotSubclass")
 @DoNotMock("Use the methods in Futures (like immediateFuture) or SettableFuture")
 /*
  * It would make sense to also annotate this class with @ElementTypesAreNonnullByDefault. However,

guava/src/com/google/common/util/concurrent/ListenableFutureTask.java

@@ -40,7 +40,6 @@
  * @author Sven Mawson
  * @since 1.0
  */
-@SuppressWarnings("ShouldNotSubclass")
 @GwtIncompatible
 @ElementTypesAreNonnullByDefault
 public class ListenableFutureTask<V extends @Nullable Object> extends FutureTask<V>

guava/src/com/google/common/util/concurrent/ListenableScheduledFuture.java

@@ -27,7 +27,6 @@
  */
 @Beta
 @GwtCompatible
-@SuppressWarnings("ShouldNotSubclass")
 @ElementTypesAreNonnullByDefault
 public interface ListenableScheduledFuture<V extends @Nullable Object>
     extends ScheduledFuture<V>, ListenableFuture<V> {}

guava/src/com/google/common/util/concurrent/ServiceManager.java

@@ -875,10 +875,8 @@ protected void doStop() {
   }
 
   /** This is never thrown but only used for logging. */
-  @SuppressWarnings("ShouldNotSubclass")
   private static final class EmptyServiceManagerWarning extends Throwable {}
 
-  @SuppressWarnings("ShouldNotSubclass")
   private static final class FailedService extends Throwable {
     FailedService(Service service) {
       super(