Merge branch 'el-cleanup-arkose-labs-trial-signup-challenge-ff' into 'master'

Remove arkose_labs_trial_signup_challenge feature flag

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/144834



Merged-by: Tetiana Chupryna <tchupryna@gitlab.com>
Approved-by: Ross Byrne <robyrne@gitlab.com>
Approved-by: Tetiana Chupryna <tchupryna@gitlab.com>
Co-authored-by: Eugie Limpin <elimpin@gitlab.com>