Fix a couple of cross-references for custom-domain

Author: benjaoming

docs/user/localization.rst

@@ -51,7 +51,7 @@ It also gets included in the Read the Docs flyout:
 .. note::
     The default language of a custom domain is determined by the language of the
     parent project that the domain was configured on. See
-    :doc:`custom_domains` for more information.
+    :doc:`/custom-domains` for more information.
 
 .. note:: You can include multiple translations in the same repository,
           with same ``conf.py`` and ``.rst`` files,

docs/user/security.rst

@@ -69,7 +69,7 @@ The issue was found by the Read the Docs team.
 Version 5.14.0
 ~~~~~~~~~~~~~~
 
-:ref:`changelog:Version 5.14.0` fixes an issue where that affected new code that removed multiple slashes in URL paths. The issue allowed the creation of hyperlinks that looked like they would go to a documentation domain on Read the Docs (either `*.readthedocs.io` or a [custom docs domain](https://docs.readthedocs.io/en/stable/custom_domains.html)) but instead went to a different domain.
+:ref:`changelog:Version 5.14.0` fixes an issue where that affected new code that removed multiple slashes in URL paths. The issue allowed the creation of hyperlinks that looked like they would go to a documentation domain on Read the Docs (either `*.readthedocs.io` or a :doc:`custom docs domain </custom-domains>`)) but instead went to a different domain.
 
 This issue was reported by Splunk after it was reported by a security audit.
 

docs/user/single_version.rst

@@ -26,6 +26,6 @@ rather than redirecting to ``https://pip.readthedocs.io/en/latest/``.
 .. warning::
 
    Documentation at ``/<language>/<default_version>/`` will stop working.
-   Remember to set :ref:`custom_domains:Canonical URLs`
+   Remember to set :doc:`canonical URLs </canonical-urls>`
    to tell search engines like Google what to index,
    and to create :doc:`user-defined-redirects` to avoid broken incoming links.