Merge branch 'bm/allowlist-oidc-auth' into 'master'

docs: add information on using OIDC with GitLab Dedicated

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/164211



Merged-by: Lysanne Pinto <lpinto@gitlab.com>
Approved-by: Oriol Lluch <olluch@gitlab.com>
Approved-by: Lysanne Pinto <lpinto@gitlab.com>
Reviewed-by: Lysanne Pinto <lpinto@gitlab.com>
Co-authored-by: bmckitrick <bmckitrick@gitlab.com>
Co-authored-by: Chris Balane <cbalane@gitlab.com>