Update gitlab-docs maintainer list for eng page update

Why is this change being made?

The GitLab Docs section of the Engineering Projects page was out-of-date, and needed to be updated to reflect the maintainer status of the Static Site Editor team. This was also an opportunity to ensure that all of the TWs were listed correctly as being associated with "doc".

This MR enables CODEOWNER updates relating to the gitlab docs project (gitlab-org/gitlab-docs!1075 (merged)), as the Engineering Project page is the system of record, and the basis of any CODEOWNER changes.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per [say-why-not-just-what][transparency]
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to your manager.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in [#mr-buddies][mr-buddies-slack].
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files.