Update black, and run auto formatting over the codebase (#9381)

- Update black version to the latest
 - Run black auto formatting over the codebase
    - Run autoformatting according to [`docs/code_style.md
`](80d6dc9783/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

synapse/replication/http/membership.py

@@ -160,7 +160,10 @@ class ReplicationRemoteRejectInviteRestServlet(ReplicationEndpoint):
 
         # hopefully we're now on the master, so this won't recurse!
         event_id, stream_id = await self.member_handler.remote_reject_invite(
-            invite_event_id, txn_id, requester, event_content,
+            invite_event_id,
+            txn_id,
+            requester,
+            event_content,
         )
 
         return 200, {"event_id": event_id, "stream_id": stream_id}