Suppress warnings in delegatingScheduled code (#4898)

* Suppress warnings in delegatingScheduled code

* fix gjf

Author: rlazo

firebase-common/src/main/java/com/google/firebase/concurrent/DelegatingScheduledExecutorService.java

@@ -124,6 +124,7 @@ public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit)
   }
 
   @Override
+  @SuppressWarnings("FutureReturnValueIgnored")
   public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
     return new DelegatingScheduledFuture<>(
         completer ->

firebase-common/src/main/java/com/google/firebase/concurrent/DelegatingScheduledFuture.java

@@ -24,6 +24,7 @@
 // going to be removed. In this case it's required since we need to implement a ScheduledFuture so
 // we can't use CallbackToFutureAdapter.
 @SuppressLint("RestrictedApi")
+@SuppressWarnings("RestrictTo")
 class DelegatingScheduledFuture<V> extends AbstractResolvableFuture<V>
     implements ScheduledFuture<V> {