Bug 1888878 - Remove obsolete comment; r=dom-storage-reviewers,asuth

Differential Revision: https://phabricator.services.mozilla.com/D206227

dom/indexedDB/IndexedDatabaseManager.cpp

@@ -611,12 +611,6 @@ nsresult IndexedDatabaseManager::BlockAndGetFileReferences(
 
     BackgroundUtilsChild* actor = new BackgroundUtilsChild(this);
 
-    // We don't set event target for BackgroundUtilsChild because:
-    // 1. BackgroundUtilsChild is a singleton.
-    // 2. SendGetFileReferences is a sync operation to be returned asap if
-    // unlabeled.
-    // 3. The rest operations like DeleteMe/__delete__ only happens at shutdown.
-    // Hence, we should keep it unlabeled.
     mBackgroundActor = static_cast<BackgroundUtilsChild*>(
         bgActor->SendPBackgroundIndexedDBUtilsConstructor(actor));
   }