Fix timetable list if parent groups are grades

aleksis/apps/chronos/util/chronos_helpers.py

@@ -104,11 +104,9 @@ def get_classes(user: "User"):
         Group.objects.for_current_school_term_or_all()
         .annotate(
             lessons_count=Count("lesson_events"),
-            child_lessons_count=Count("child_groups__lesson_events"),
         )
         .filter(
-            Q(lessons_count__gt=0, parent_groups=None)
-            | Q(child_lessons_count__gt=0, parent_groups=None)
+            Q(lessons_count__gt=0)
         )
         .order_by("short_name", "name")
     )