Fix for **Use unique domain** setting changes in URLs

What does this MR do and why?

Add the new URL scheme based on Use unique domain feature flag, now enabled by default.

Potential fix for #436931 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Current page is https://docs.gitlab.com/16.7/ee/user/project/pages/getting_started_part_one.html

How to set up and validate locally