Update executor.py

Author: femesq

graphql/execution/experimental/executor.py

@@ -18,7 +18,6 @@ def execute(schema, document_ast, root_value=None, context_value=None,
     if middleware:
         if not isinstance(middleware, MiddlewareManager):
             middleware = MiddlewareManager(*middleware)
-            
         assert isinstance(middleware, MiddlewareManager), (
             'middlewares have to be an instance'
             ' of MiddlewareManager. Received "{}".'.format(middleware)