Update notification when timeline changes

Notification buttons for next/previous should change based on the new index of the currently played media item after another media item is added or removed from a playlist.

Issue: androidx/media#130
PiperOrigin-RevId: 485869144

libraries/session/src/main/java/androidx/media3/session/MediaNotificationManager.java

@@ -294,7 +294,8 @@ import java.util.concurrent.TimeoutException;
       if (events.containsAny(
           Player.EVENT_PLAYBACK_STATE_CHANGED,
           Player.EVENT_PLAY_WHEN_READY_CHANGED,
-          Player.EVENT_MEDIA_METADATA_CHANGED)) {
+          Player.EVENT_MEDIA_METADATA_CHANGED,
+          Player.EVENT_TIMELINE_CHANGED)) {
         mediaSessionService.onUpdateNotification(session);
       }
     }