Archive project in favor or pages/gatsby

We should archive this project in favor of https://gitlab.com/pages/gatsby.

• This project is Not used as a built-in project template, so it's effectively a duplicate of https://gitlab.com/pages/gatsby. You can see the repo URL of the Gatsby template in https://gitlab.com/gitlab-org/gitlab/-/blob/33008f2938804affe66025d4b699f8fece95d309/lib/gitlab/project_template.rb#L64.
• It's not updated that often.