minor #17819 Fix small typo in notifier.rst (pchr-srf)

This PR was submitted for the 6.2 branch but it was merged into the 5.4 branch instead.

Discussion
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Fix small typo in notifier.rst

Merci!

Commits
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3dbb4ab Update notifier.rst

Author: javiereguiluz

notifier.rst

@@ -332,7 +332,7 @@ you to send messages to chat services::
         public function thankyou(ChatterInterface $chatter)
         {
             $message = (new ChatMessage('You got a new invoice for 15 EUR.'))
-                // if not set explicitly, the message is send to the
+                // if not set explicitly, the message is sent to the
                 // default transport (the first one configured)
                 ->transport('slack');