Merge branch '497375-cleanup-duo-free-access-ending-banner' into 'master'

Cleanup duo_free_access_ending_banner feature flag

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/170868



Merged-by: Doug Stull <dstull@gitlab.com>
Approved-by: Chaoyue Zhao <czhao@gitlab.com>
Approved-by: Scott Hampton <shampton@gitlab.com>
Approved-by: Jay Montal <jmontal@gitlab.com>
Approved-by: Doug Stull <dstull@gitlab.com>
Reviewed-by: Jay Montal <jmontal@gitlab.com>
Reviewed-by: Chaoyue Zhao <czhao@gitlab.com>
Co-authored-by: Buck OLeary <bucoleary@gitlab.com>