Remove room_version param from check_auth_rules_for_event

Instead, use the `room_version` property of the event we're checking.

The `room_version` was originally added as a parameter somewhere around #4482,
but really it's been redundant since #6875 added a `room_version` field to `EventBase`.

synapse/state/v1.py

@@ -30,7 +30,7 @@ from typing import (
 from synapse import event_auth
 from synapse.api.constants import EventTypes
 from synapse.api.errors import AuthError
-from synapse.api.room_versions import RoomVersion, RoomVersions
+from synapse.api.room_versions import RoomVersion
 from synapse.events import EventBase
 from synapse.types import MutableStateMap, StateMap
 
@@ -331,7 +331,6 @@ def _resolve_auth_events(
         try:
             # The signatures have already been checked at this point
             event_auth.check_auth_rules_for_event(
-                RoomVersions.V1,
                 event,
                 auth_events.values(),
             )
@@ -349,7 +348,6 @@ def _resolve_normal_events(
         try:
             # The signatures have already been checked at this point
             event_auth.check_auth_rules_for_event(
-                RoomVersions.V1,
                 event,
                 auth_events.values(),
             )

synapse/state/v2.py

@@ -547,7 +547,6 @@ async def _iterative_auth_checks(
 
         try:
             event_auth.check_auth_rules_for_event(
-                room_version,
                 event,
                 auth_events.values(),
             )