Remove no longer needed type ignore comment

Author: Fizzadar

synapse/storage/databases/main/event_federation.py

@@ -1187,7 +1187,7 @@ async def get_forward_extremities_for_room_at_stream_ordering(
         """
         # We want to make the cache more effective, so we clamp to the last
         # change before the given ordering.
-        last_change = self._events_stream_cache.get_max_pos_of_last_change(room_id)  # type: ignore[attr-defined]
+        last_change = self._events_stream_cache.get_max_pos_of_last_change(room_id)
 
         # We don't always have a full stream_to_exterm_id table, e.g. after
         # the upgrade that introduced it, so we make sure we never ask for a