Merge branch '6.4' into 7.0

* 6.4:
  [Mailer] Updated webhook support in Mailer bridge overview for 6.4

Author: OskarStark

mailer.rst

@@ -114,7 +114,7 @@ Service               Install with                                    Webhook su
 `Mandrill`_           ``composer require symfony/mailchimp-mailer``
 `Postmark`_           ``composer require symfony/postmark-mailer``    yes
 `Scaleway`_           ``composer require symfony/scaleway-mailer``
-`SendGrid`_           ``composer require symfony/sendgrid-mailer``
+`SendGrid`_           ``composer require symfony/sendgrid-mailer``    yes
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 .. note::