LoggingTransaction accepts None for callback lists.

Its a bit disingenuousto give LoggingTransaction lists to append
callbacks to if we're not going to run the callbacks.

synapse/storage/event_push_actions.py

@@ -79,8 +79,6 @@ class EventPushActionsWorkerStore(SQLBaseStore):
             db_conn.cursor(),
             name="_find_stream_orderings_for_times_txn",
             database_engine=self.database_engine,
-            after_callbacks=[],
-            exception_callbacks=[],
         )
         self._find_stream_orderings_for_times_txn(cur)
         cur.close()