minor #12879 Update service id of the MailerInterface (rosier)

This PR was merged into the 4.3 branch.

Discussion
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Update service id of the MailerInterface

The service id of the MailerInterface was changed in symfony/symfony#31854 to avoid an conflict with SwiftMailer

Commits
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93668de Update service id of the MailerInterface

Author: javiereguiluz

mailer.rst

@@ -93,7 +93,7 @@ Creating & Sending Messages
 ---------------------------
 
 To send an email, autowire the mailer using
-:class:`Symfony\\Component\\Mailer\\MailerInterface` (service id ``mailer``)
+:class:`Symfony\\Component\\Mailer\\MailerInterface` (service id ``mailer.mailer``)
 and create an :class:`Symfony\\Component\\Mime\\Email` object::
 
     // src/Controller/MailerController.php