fix(database): remove sync on stream broadcast (#13503)

Co-authored-by: Russell Wheatley <russellwheatley85@gmail.com>

Author: SelaseKay

packages/firebase_database/firebase_database_web/lib/src/interop/database.dart

@@ -482,7 +482,6 @@ class Query<T extends database_interop.QueryJsImpl> extends JsObjectWrapper<T> {
     streamController = StreamController<QueryEvent>.broadcast(
       onListen: startListen,
       onCancel: stopListen,
-      sync: true,
     );
     return streamController.stream;
   }