Fix j2kt stream package nullability

Fix sort() parameter nullability

RELNOTES=n/a
PiperOrigin-RevId: 538560615

Author: stefanhaustein

guava/src/com/google/common/collect/ImmutableList.java

@@ -577,7 +577,7 @@ public final void replaceAll(UnaryOperator<E> operator) {
   @Deprecated
   @Override
   @DoNotCall("Always throws UnsupportedOperationException")
-  public final void sort(Comparator<? super E> c) {
+  public final void sort(@Nullable Comparator<? super E> c) {
     throw new UnsupportedOperationException();
   }
 

guava/src/com/google/common/collect/Synchronized.java

@@ -447,7 +447,7 @@ public void replaceAll(UnaryOperator<E> operator) {
     }
 
     @Override
-    public void sort(Comparator<? super E> c) {
+    public void sort(@Nullable Comparator<? super E> c) {
       synchronized (mutex) {
         delegate().sort(c);
       }