Merge branch 'revert-feature-flag-check-frame-src-policy' into 'master'

Remove feature flag check on frame-src policy

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/106772



Merged-by: David O'Regan <doregan@gitlab.com>
Approved-by: David O'Regan <doregan@gitlab.com>
Co-authored-by: Enrique Alcantara <ealcantara@gitlab.com>