Clean-up events persistance code (#14411)

By removing unused variables and making some arguments
required which are always provided.

changelog.d/14411.misc

@@ -0,0 +1 @@
+Clean-up event persistence code.

synapse/storage/controllers/persist_events.py

@@ -716,8 +716,6 @@ async def _persist_event_batch(
                             )
                             if not is_still_joined:
                                 logger.info("Server no longer in room %s", room_id)
-                                latest_event_ids = set()
-                                current_state = {}
                                 delta.no_longer_in_room = True
 
                             state_delta_for_room[room_id] = delta

synapse/storage/databases/main/events.py

@@ -355,9 +355,9 @@ def _persist_events_txn(
         txn: LoggingTransaction,
         *,
         events_and_contexts: List[Tuple[EventBase, EventContext]],
-        inhibit_local_membership_updates: bool = False,
-        state_delta_for_room: Optional[Dict[str, DeltaState]] = None,
-        new_forward_extremities: Optional[Dict[str, Set[str]]] = None,
+        inhibit_local_membership_updates: bool,
+        state_delta_for_room: Dict[str, DeltaState],
+        new_forward_extremities: Dict[str, Set[str]],
     ) -> None:
         """Insert some number of room events into the necessary database tables.
 
@@ -384,9 +384,6 @@ def _persist_events_txn(
             PartialStateConflictError: if attempting to persist a partial state event in
                 a room that has been un-partial stated.
         """
-        state_delta_for_room = state_delta_for_room or {}
-        new_forward_extremities = new_forward_extremities or {}
-
         all_events_and_contexts = events_and_contexts
 
         min_stream_order = events_and_contexts[0][0].internal_metadata.stream_ordering