Merge branch 'docs-update-self-managed-5' into 'master'

Update self-managed terminology in several docs dirs

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/180000



Merged-by: Suzanne Selhorn <sselhorn@gitlab.com>
Approved-by: Amy Qualls <aqualls@gitlab.com>
Co-authored-by: Marcel Amirault <mamirault@gitlab.com>