🔥(backend) remove todo items

The Pylint job was failing due to those TODO items. In our make lint
command sequence, Pylint runs first. If it fails, Ruff won't run,
which is quite inconvenient.

I've extracted those TODOs into an issue for further review.

src/backend/core/api/viewsets.py

@@ -209,7 +209,6 @@ class RoomViewSet(
         user = self.request.user
 
         if user.is_authenticated:
-            # todo - simplify this queryset
             queryset = (
                 self.filter_queryset(self.get_queryset())
                 .filter(Q(users=user))