remove types index specification because it is not compatible with later versions of mongodb

apps/notifications/models.py

@@ -69,8 +69,7 @@ class MUserFeedNotification(mongo.Document):
         'collection': 'notifications',
         'indexes': ['feed_id',
                     {'fields': ['user_id', 'feed_id'], 
-                     'unique': True,
-                     'types': False,
+                     'unique': True
                     }],
         'allow_inheritance': False,
     }