Adjust permission names to Room migration

Closes #199 (closed)

And there is migration 0005 that contains that permission name. Does this migration need to be edited?

aleksis/apps/chronos/util/chronos_helpers.py

@@ -152,7 +152,7 @@ def get_rooms(user: "User"):
         wanted_rooms = set()
 
         for room in rooms:
-            if checker.has_perm("chronos.view_room_timetable", room):
+            if checker.has_perm("core.view_room_timetable", room):
                 wanted_rooms.add(room.pk)
 
         rooms = rooms.filter(Q(pk__in=wanted_rooms))