Fix typo

Author: pierredup

messenger.rst

@@ -2082,7 +2082,7 @@ Sometimes, you may need to regularly ping a webservice to get its status, e.g.
 is it up or down. It is possible to do so by dispatching a
 :class:`Symfony\\Component\\HttpClient\\Messenger\\PingWebhookMessage`::
 
-    use Symfony\Component\HttpClient\Messenger\RPingWebhookMessage;
+    use Symfony\Component\HttpClient\Messenger\PingWebhookMessage;
     use Symfony\Component\Messenger\MessageBusInterface;
 
     class LivenessService