minor symfony#12725 Update mailer.rst (atailouloute)

This PR was squashed before being merged into the 4.4 branch (closes symfony#12725).

Discussion
----------

Update mailer.rst

Commits
-------

627ec43 Update mailer.rst

Author: OskarStark

components/mailer.rst

@@ -64,10 +64,10 @@ it:
 
 Then, use the SMTP Gmail transport::
 
-    use Symfony\Component\Mailer\Bridge\Google\Smtp\GmailTransport;
+    use Symfony\Component\Mailer\Bridge\Google\Transport\GmailSmtpTransport;
     use Symfony\Component\Mailer\Mailer;
 
-    $transport = new GmailTransport('user', 'pass');
+    $transport = new GmailSmtpTransport('user', 'pass');
     $mailer = new Mailer($transport);
     $mailer->send($email);