Merge branch '5.1' into 5.2

* 5.1:
  Update messenger.rst

Author: OskarStark

messenger.rst

@@ -213,7 +213,7 @@ you can configure them to be sent to a transport:
 
                 routing:
                     # async is whatever name you gave your transport above
-                    'App\Message\SmsNotification':  async
+                    'App\Message\SmsNotification': async
 
     .. code-block:: xml