Link in the blog post about custom domains for Pages is not working for external users

In the blog post at https://about.gitlab.com/2018/02/05/gitlab-pages-custom-domain-validation/ we have a link to https://gitlab.com/gitlab-org/gitlab-ce/issues/29497, but this issues is confidential and cannot be accessed by any external user.

We should both make the issue public, or change the blog post.