Follow-up from "Add KAS URL configuration"

The following discussion from !1842 (merged) should be addressed:

• @ashmckenzie started a discussion:

  thought: Should this be documented, perhaps at https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/master/doc/howto/kubernetes_agent.md and/or https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/master/doc/configuration.md ?