fix async routine

Author: giancarloromeo

services/storage/src/simcore_service_storage/modules/celery/client.py

@@ -81,7 +81,7 @@ async def abort_task(self, task_context: TaskContext, task_uuid: TaskUUID) -> No
             await self._abort_task(task_context, task_uuid)
 
     @make_async()
-    async def _forget_task(self, task_id: TaskID) -> None:
+    def _forget_task(self, task_id: TaskID) -> None:
         AbortableAsyncResult(task_id, app=self._celery_app).forget()
 
     async def get_task_result(