Fix which domain should be added to PSL

It references the issue where gitlab.io was added to the PSL saying `*.gitlab.io` was added to the PSL, but it was in fact `gitlab.io`.

Originally submitted at
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/5301.
Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/administration/pages/index.md

@@ -74,8 +74,8 @@ among other things.
 
 Follow [these instructions](https://publicsuffix.org/submit/) to submit your
 GitLab Pages subdomain. For instance, if your domain is `example.io`, you should
-request that `*.example.io` is added to the Public Suffix List. GitLab.com
-added `*.gitlab.io` [in 2016](https://gitlab.com/gitlab-com/infrastructure/issues/230).
+request that `example.io` is added to the Public Suffix List. GitLab.com
+added `gitlab.io` [in 2016](https://gitlab.com/gitlab-com/infrastructure/issues/230).
 
 ### DNS configuration