Add missing new line

Author: patrick91

graphene_django/rest_framework/mutation.py

@@ -126,4 +126,4 @@ def mutate(cls, instance, args, request, info):
     def perform_mutate(cls, serializer, info):
         obj = serializer.save()
 
-        return cls(errors=[], **obj)
+        return cls(errors=[], **obj)