Remove superfluous room_memberships join from background update

Spawning from #15731

synapse/storage/databases/main/roommember.py

@@ -1461,7 +1461,6 @@ def add_membership_profile_txn(txn: LoggingTransaction) -> int:
                 SELECT stream_ordering, event_id, events.room_id, event_json.json
                 FROM events
                 INNER JOIN event_json USING (event_id)
-                INNER JOIN room_memberships USING (event_id)
                 WHERE ? <= stream_ordering AND stream_ordering < ?
                 AND type = 'm.room.member'
                 ORDER BY stream_ordering DESC