remove superfluous cache invalidations

Author: reivilibre

synapse/storage/databases/main/thread_subscriptions.py

@@ -165,12 +165,6 @@ def _subscribe_user_to_thread_txn(txn: LoggingTransaction) -> Optional[int]:
                 values=values,
             )
 
-            self._invalidate_cache_and_stream(
-                txn,
-                self.get_subscription_for_thread,
-                (user_id, room_id, thread_root_event_id),
-            )
-
             return stream_id
 
         return await self.db_pool.runInteraction(
@@ -230,12 +224,6 @@ def _unsubscribe_user_from_thread_txn(txn: LoggingTransaction) -> Optional[int]:
                 },
             )
 
-            self._invalidate_cache_and_stream(
-                txn,
-                self.get_subscription_for_thread,
-                (user_id, room_id, thread_root_event_id),
-            )
-
             return stream_id
 
         return await self.db_pool.runInteraction(