Add requester arg to send_membership_event, remove arg in remote_reject_invite

changelog.d/6009.misc

@@ -0,0 +1 @@
+Small refactor of function arguments and docstrings in RoomMemberHandler.

synapse/handlers/room_member.py

@@ -491,6 +491,8 @@ def _update_membership(
                 else:
                     # send the rejection to the inviter's HS.
                     remote_room_hosts = remote_room_hosts + [inviter.domain]
+                    # Note: This is calling _remote_reject_invite on RoomMemberMasterHandler,
+                    # hence the `requester` arg
                     res = yield self._remote_reject_invite(
                         requester, remote_room_hosts, room_id, target
                     )
@@ -510,9 +512,7 @@ def _update_membership(
         return res
 
     @defer.inlineCallbacks
-    def send_membership_event(
-        self, requester, event, context, remote_room_hosts=None, ratelimit=True
-    ):
+    def send_membership_event(self, requester, event, context, ratelimit=True):
         """
         Change the membership status of a user in a room.
 
@@ -522,16 +522,10 @@ def send_membership_event(
                 act as the sender, will be skipped.
             event (SynapseEvent): The membership event.
             context: The context of the event.
-            is_guest (bool): Whether the sender is a guest.
-            room_hosts ([str]): Homeservers which are likely to already be in
-                the room, and could be danced with in order to join this
-                homeserver for the first time.
             ratelimit (bool): Whether to rate limit this request.
         Raises:
             SynapseError if there was a problem changing the membership.
         """
-        remote_room_hosts = remote_room_hosts or []
-
         target_user = UserID.from_string(event.state_key)
         room_id = event.room_id