Merge branch 'gmh-remove-duo-ask-feature-flag' into 'master'

Remove move_git_service_to_ai_gateway feature flag

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/159150



Merged-by: James Fargher <jfargher@gitlab.com>
Approved-by: Ian Anderson <ianderson@gitlab.com>
Approved-by: Hinam Mehra <hmehra@gitlab.com>
Approved-by: James Fargher <jfargher@gitlab.com>
Reviewed-by: Ian Anderson <ianderson@gitlab.com>
Co-authored-by: Gary Holtz <gholtz@gitlab.com>