Knative domain name/endpoint section links to invalid doc

The More Information link points here: https://gitlab.com/help/user/project/clusters/index.md#manually-determining-the-external-endpoint, but there is no section on the page for manually-determining-the-external-endpoint anymore.

Definition of Done

• Fix Documentation on https://gitlab.com/help/user/project/clusters/index.md so it clearly explains how to point a wildcard DNS to the Knative Endpoint
• Ensure link points to correct place in documentation