[5.0.x] Used more specific link to email backends in EMAIL_BACKEND docs.

Backport of 1592f0ac220c1fd37779f6d33efb28ebd60e2e66 from main

docs/ref/settings.txt

@@ -1408,7 +1408,7 @@ This is only used if ``CommonMiddleware`` is installed (see
 Default: ``'``:class:`django.core.mail.backends.smtp.EmailBackend`\ ``'``
 
 The backend to use for sending emails. For the list of available backends see
-:doc:`/topics/email`.
+:ref:`topic-email-backends`.
 
 .. setting:: EMAIL_FILE_PATH