Revert "Removing unused types key from index."

This reverts commit 6b384b51a2.

apps/notifications/models.py

@@ -38,6 +38,7 @@ class MUserNotificationTokens(mongo.Document):
         'collection': 'notification_tokens',
         'indexes': [{'fields': ['user_id'], 
                      'unique': True,
+                     'types': False,
                     }],
         'allow_inheritance': False,
     }