Do not use settings.INSTALLEDA_APPS in migration

aleksis/core/migrations/0046_add_room_model.py

 # Generated by Django 3.2.15 on 2022-11-20 14:20
 
-from django.conf import settings
+from django.apps import apps
 import django.contrib.sites.managers
 from django.db import migrations, models
 import django.db.models.deletion
@@ -16,7 +16,7 @@ class Migration(migrations.Migration):
         ('core', '0045_data_check_result_fix_check_field'),
     ]
 
-    if "aleksis.apps.chronos.apps.ChronosConfig" in settings.INSTALLED_APPS:
+    if "chronos" in apps.app_configs:
         recorder = migrations.recorder
         if not recorder.MigrationRecorder.Migration.objects.filter(app="core", name="0046_add_room_model").exists():
             dependencies.append(('chronos', '0012_add_supervision_global_permission'))
@@ -48,7 +48,7 @@ class Migration(migrations.Migration):
         # Migrate data from Chronos table; deletion will be handled by Chronos
         migrations.RunSQL(
             """
-            -- Use a temporary, empty source table in case Chronos is not installed
+            -- Copy rooms from chronos if table exists
             DO $$BEGIN INSERT INTO core_room SELECT * FROM chronos_room; EXCEPTION WHEN undefined_table THEN NULL; END$$;
             """
         ),