[Mailer] Updated heading for require_tls option

Author: ssddanbrown

mailer.rst

@@ -420,8 +420,8 @@ setting the ``auto_tls`` option to ``false`` in the DSN::
 
     This setting only works when the ``smtp://`` protocol is used.
 
-Require use of TLS
-~~~~~~~~~~~~~~~~~~
+Ensure TLS
+~~~~~~~~~~
 
 You may want to ensure TLS is used, either directly or via ``STARTTLS``,
 for sending mail over SMTP regardless of other options set or SMTP server