Fix bad naming of storage function (#9637)

We had two functions named `get_forward_extremities_for_room` and
`get_forward_extremeties_for_room` that took different paramters. We
rename one of them to avoid confusion.

changelog.d/9637.misc

+Rename storage function to fix spelling and not conflict with another functions name.

synapse/handlers/device.py

@@ -166,7 +166,7 @@ class DeviceWorkerHandler(BaseHandler):
 
             # Fetch the current state at the time.
             try:
-                event_ids = await self.store.get_forward_extremeties_for_room(
+                event_ids = await self.store.get_forward_extremities_for_room_at_stream_ordering(
                     room_id, stream_ordering=stream_ordering
                 )
             except errors.StoreError:

synapse/handlers/sync.py

@@ -1979,8 +1979,10 @@ class SyncHandler:
 
             logger.info("User joined room after current token: %s", room_id)
 
-            extrems = await self.store.get_forward_extremeties_for_room(
-                room_id, event_pos.stream
+            extrems = (
+                await self.store.get_forward_extremities_for_room_at_stream_ordering(
+                    room_id, event_pos.stream
+                )
             )
             users_in_room = await self.state.get_current_users_in_room(room_id, extrems)
             if user_id in users_in_room:

synapse/storage/databases/main/event_federation.py

@@ -793,7 +793,7 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
 
         return int(min_depth) if min_depth is not None else None
 
-    async def get_forward_extremeties_for_room(
+    async def get_forward_extremities_for_room_at_stream_ordering(
         self, room_id: str, stream_ordering: int
     ) -> List[str]:
         """For a given room_id and stream_ordering, return the forward