minor #15199 [Messenger] fix typo (xabbuh)

This PR was merged into the 4.4 branch.

Discussion
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[Messenger] fix typo

Commits
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5c20fe3 [Messenger] fix typo

Author: wouterj

messenger.rst

@@ -316,7 +316,7 @@ to multiple transports:
 
 .. note::
 
-    If you configure routing for both a child and parent class, but rules
+    If you configure routing for both a child and parent class, both rules
     are used. E.g. if you have an ``SmsNotification`` object that extends
     from ``Notification``, both the routing for ``Notification`` and
     ``SmsNotification`` will be used.