Update mercure.rst

Co-Authored-By: dunglas <[email protected]>

Author: OskarStark

mercure.rst

@@ -243,7 +243,7 @@ and to configure properly a transport (if you don't, the handler will
 be called synchronously).
 
 Then, dispatch the Mercure ``Update`` to the Messenger's Message Bus,
-it will be handled automatically:
+it will be handled automatically::
 
     // src/Controller/PublishController.php
     namespace App\Controller;