Minor reword

Author: javiereguiluz

messenger.rst

@@ -451,9 +451,9 @@ that you can inject in your services.
 
 .. note::
 
-    To register a handler for only a specific bus, add a ``bus`` attribute having the
-    name of this bus as value to the ``messenger.message_handler`` tag in the handler's
-    service definition.
+    To register a handler only for a specific bus, add a ``bus`` attribute to
+    the handler's service tag (``messenger.message_handler``) and use the bus
+    name as its value.
 
 Type-hints and Auto-wiring
 ~~~~~~~~~~~~~~~~~~~~~~~~~~