Merge branch '280597-update-milestone-events-when-promoting' into 'master'

Update milestone events when promoting milestones

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/140158



Merged-by: Siddharth Dungarwal <sdungarwal@gitlab.com>
Approved-by: Michael Becker <11881043-wandering_person@users.noreply.gitlab.com>
Approved-by: Siddharth Dungarwal <sdungarwal@gitlab.com>
Reviewed-by: Michael Becker <11881043-wandering_person@users.noreply.gitlab.com>
Co-authored-by: Heinrich Lee Yu <heinrich@gitlab.com>