Sync config v13.9.0 : Update links to redirected docs

Just updating link in comment
See corresponding Merge request
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/53004

Author: kkimurak

assets/runtime/config/gitlabhq/gitlab.yml

@@ -506,7 +506,7 @@ production: &base
   ## Gravatar
   ## If using gravatar.com, there's nothing to change here. For Libravatar
   ## you'll need to provide the custom URLs. For more information,
-  ## see: https://docs.gitlab.com/ee/customization/libravatar.html
+  ## see: https://docs.gitlab.com/ee/administration/libravatar.html
   gravatar:
     enabled: {{GITLAB_GRAVATAR_ENABLED}}
     # Gravatar/Libravatar URLs: possible placeholders: %{hash} %{size} %{email} %{username}