minor #10582 Fix Use Class (ahinkle)

This PR was merged into the 4.1 branch.

Discussion
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Fix Use Class

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Commits
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d303258 Fix Use Class

Author: javiereguiluz

messenger.rst

@@ -49,7 +49,7 @@ message handler. It's a class with an ``__invoke`` method::
     // src/MessageHandler/MyMessageHandler.php
     namespace App\MessageHandler;
 
-    use Symfony\Component\Messenger\Handler;
+    use Symfony\Component\Messenger\Handler\MessageHandlerInterface;
 
     class MyMessageHandler implements MessageHandlerInterface
     {