Minor: Remove extra space in the config example

Author: bocharsky-bw

mailer.rst

@@ -962,7 +962,7 @@ you have a transport called ``async``, you can route the message there:
                     async: "%env(MESSENGER_TRANSPORT_DSN)%"
 
                 routing:
-                    'Symfony\Component\Mailer\Messenger\SendEmailMessage':  async
+                    'Symfony\Component\Mailer\Messenger\SendEmailMessage': async
 
     .. code-block:: xml