Adapt to managed_by change

aleksis/apps/alsijil/preferences.py

@@ -102,6 +102,3 @@ class GroupTypePriorityCoursebook(ModelChoicePreference):
         "select field on the coursebook overview page"
     )
     help_text = _("If you leave it empty, no group type will be used.")
-
-    def get_queryset(self):
-        return GroupType.objects.managed_and_unmanaged()