Create faux group for Tutorials, update pages

What does this MR do?

Kati would like to be pinged on changes in the doc/tutorials folder. Manual changes to the TW portion of the CODEOWNERS file are unlikely to persist after someone performs the update steps listed at https://docs.gitlab.com/ee/development/documentation/#batch-updates-for-tw-metadata.

The easiest approach would be to add a faux group for Tutorials, assign it to Kati in the Rake task, and her request will persist. This change would have a small ripple effect on Suzanne's content audit spreadsheet, but from a Slack discussion this morning, it sounds minimal.

Related issues (original)

• Closes Create custom stage / group for tutorials section (technical-writing#672 - closed)
• Related to Update CODEOWNERS with new paths (!96697 - merged) where the need was identified

Related issues

These issues and MRs describe the evolution of the CODEOWNERS project for the Technical Writing team, from the initial idea through multiple (!) iterations to a finished product. These links may have been added significantly after this issue or merge request was closed, so they may describe parts of the process before or after this work.

• Related to Create rake task for docs CODEOWNERS (!77715 - merged) where Amy had an idea
• Related to Update CODEOWNERS to include TW assignments for... (!77606 - merged) where we asked for the raw output of the Rake task to be added into the CODEOWNERS file. This rake task would give the TW team a way to periodically generate a full list of owned pages.
• Related to Expand CODEOWNERS with more documentation DRIs (#349587 - closed) where Marcel noted many pages needed a DRI declared
• Related to Update CODEOWNERS to include TW assignments for... (!77606 - merged) where we started manually shortening the results
• Related to Refine how to run batch updates for the CODEOWN... (technical-writing#668 - closed) where we started figuring out how to run batch updates
• Related to Codeowners: Assign TW with more than 50% page o... (#375783 - closed) where we started automating the process of shortening and condensing the results
• Related to Document tw::codeowners rake task (technical-writing#598 - closed) where we documented the task
• Related to Create custom stage / group for tutorials section (technical-writing#672 - closed) where we had to find alternate assignments for part of the docset that is owned, but not by a stage/group
• Related to Release Post 15.7 MVP Nominations (gitlab-com/www-gitlab-com#14283 - closed) where Niklas was nominated as MVP for the months of iteration needed to bring this script to a full, workable state

Author's checklist

• Optional. Consider taking the GitLab Technical Writing Fundamentals course.
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