pw_rpc: Remove the default abandon() implementation

This reverts commit c294be0, which was
a temporary workaround.

Change-Id: I865a6c7d67bc8803ad3f0e8b5e4d73b38a5d46ee
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/97747
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Alexei Frolov <frolv@google.com>

pw_rpc/java/main/dev/pigweed/pw_rpc/Call.java

@@ -24,16 +24,7 @@ public interface Call {
   void cancel() throws ChannelOutputException;
 
   /** Cancels the RPC as in cancel(), but does not send a cancellation packet to the server. */
-  default void abandon() {
-    // By default, call cancel() and ignore exceptions.
-    // TODO(b/235513314): Remove this default implementation once users have
-    //     implemented abandon().
-    try {
-      cancel();
-    } catch (ChannelOutputException e) {
-      // Ignore the exception, since abandon() isn't supposed to send packets.
-    }
-  }
+  void abandon();
 
   /** True if the RPC has not yet completed. */
   default boolean active() {