Fix: do not use current apps in migrations (#15839)

awx/main/migrations/_OrgAdmin_to_use_ig.py

@@ -1,13 +1,12 @@
 import logging
 
-from awx.main.models import Organization
-
 logger = logging.getLogger('awx.main.migrations')
 
 
 def migrate_org_admin_to_use(apps, schema_editor):
     logger.info('Initiated migration from Org admin to use role')
     roles_added = 0
+    Organization = apps.get_model('main', 'Organization')
     for org in Organization.objects.prefetch_related('admin_role__members').iterator(chunk_size=1000):
         igs = list(org.instance_groups.all())
         if not igs: