Update msg for async handler

Author: bhavin-nakrani

messenger.rst

@@ -326,7 +326,7 @@ Doctrine Entities in Messages
 
 If you need to pass a Doctrine entity in a message, it's better to pass the entity's
 primary key (or whatever relevant information the handler actually needs, like ``email``,
-etc) instead of the object::
+etc) instead of the object othwerwise it will give error regarding EntityManager not found in async handler ::
 
     // src/Message/NewUserWelcomeEmail.php
     namespace App\Message;