Add class link for AsMessageHandler

Author: mdoutreluingne

messenger.rst

@@ -1983,7 +1983,7 @@ A handler class can handle multiple messages or configure itself by implementing
 .. deprecated:: 6.2
 
     :class:`Symfony\\Component\\Messenger\\Handler\\MessageSubscriberInterface` was deprecated in Symfony 6.2.
-    Use `#[AsMessageHandler]` attribute instead.
+    Use :class:`..... <#[AsMessageHandler]>` attribute instead.
 
 Binding Handlers to Different Transports
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~