Annotate deprecated methods in ForwardingPlayer

This change is needed to generate correct javadoc, otherwise
these methods appear as not deprecated.

#minor-release

PiperOrigin-RevId: 390339092

library/common/src/main/java/com/google/android/exoplayer2/ForwardingPlayer.java

@@ -48,8 +48,8 @@ public Looper getApplicationLooper() {
     return player.getApplicationLooper();
   }
 
+  @Deprecated
   @Override
-  @SuppressWarnings("deprecation") // Implementing deprecated method.
   public void addListener(EventListener listener) {
     player.addListener(new ForwardingEventListener(this, listener));
   }
@@ -59,8 +59,8 @@ public void addListener(Listener listener) {
     player.addListener(new ForwardingListener(this, listener));
   }
 
+  @Deprecated
   @Override
-  @SuppressWarnings("deprecation") // Implementing deprecated method.
   public void removeListener(EventListener listener) {
     player.removeListener(new ForwardingEventListener(this, listener));
   }
@@ -346,8 +346,8 @@ public void stop() {
     player.stop();
   }
 
+  @Deprecated
   @Override
-  @SuppressWarnings("deprecation") // Forwarding to deprecated method.
   public void stop(boolean reset) {
     player.stop(reset);
   }