Cache instances of type InternalGroup instead of AccountGroup by UUID

Change-Id: Id4725960eb155945f0344a56e7f36d5f4293750d

gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticGroupIndex.java

@@ -213,7 +213,7 @@ public class ElasticGroupIndex extends AbstractElasticIndex<AccountGroup.UUID, I
               source.getAsJsonObject().get(GroupField.UUID.getName()).getAsString());
       // Use the GroupCache rather than depending on any stored fields in the
       // document (of which there shouldn't be any).
-      return groupCache.get().getInternalGroup(uuid);
+      return groupCache.get().get(uuid);
     }
   }
 }