Merge branch 'docs_lz_brie' into 'master'

Add guidance on allowed Geo IPs for 401 troubleshooting

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/170293



Merged-by: Suzanne Selhorn <sselhorn@gitlab.com>
Approved-by: Phillip Wells <pwells@gitlab.com>
Approved-by: Ian Baum <ibaum@gitlab.com>
Co-authored-by: luciezhao <lzhao@gitlab.com>