Merge branch 'aqualls-undocumented-test' into 'master'

Document non-Vale/markdownlint tests in lint-doc.sh

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/122359



Merged-by: Evan Read <eread@gitlab.com>
Approved-by: Marcel Amirault <mamirault@gitlab.com>
Reviewed-by: Marcel Amirault <mamirault@gitlab.com>
Co-authored-by: Marcel Amirault <mamirault@gitlab.com>
Co-authored-by: Amy Qualls <aqualls@gitlab.com>