ForwardingRemovalListener: suppress unchecked warning

Change-Id: Ic22f1bdd0731132704aec9a7182201db55ade90b
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/cache/ForwardingRemovalListener.java b/gerrit-server/src/main/java/com/google/gerrit/server/cache/ForwardingRemovalListener.java
index c98ddf9..b99648b 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/cache/ForwardingRemovalListener.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/cache/ForwardingRemovalListener.java
@@ -52,6 +52,7 @@
     }
   }
 
+  @SuppressWarnings("unchecked")
   public void onRemoval(RemovalNotification<K, V> notification) {
     for (CacheRemovalListener<K, V> l : listeners) {
       l.onRemoval(pluginName, cacheName, notification);