Remove MVP implementation of CI config chat

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/138448



Merged-by: Hordur Freyr Yngvason <hfyngvason@gitlab.com>
Approved-by: Taka Nishida <tnishida@gitlab.com>
Approved-by: Leonardo da Rosa <ldarosa@gitlab.com>
Approved-by: Hordur Freyr Yngvason <hfyngvason@gitlab.com>
Approved-by: Jarka Košanová <jarka@gitlab.com>
Reviewed-by: Leonardo da Rosa <ldarosa@gitlab.com>
Reviewed-by: Taka Nishida <tnishida@gitlab.com>
Co-authored-by: Eulyeon Ko <5961404-euko@users.noreply.gitlab.com>
Co-authored-by: Eulyeon Ko <eko@gitlab.com>