Update messenger.rst

Co-authored-by: Mata <[email protected]>

Author: sylfabre

messenger.rst

@@ -441,6 +441,7 @@ With the following code and configuration, messages will be dispatched like this
 
 .. code-block::php
     namespace App\Message;
+
     class SmsNotification extends Notification {}
 
 .. code-block::yaml