Merge branch '376293-clean-up-successful-exp-trial-email-validation' into 'master'

Cleaned up successful experiment `trial_email_validation`

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/112219



Merged-by: Michael Lunøe <michael.lunoe@gmail.com>
Approved-by: Omar Qunsul <oqunsul@gitlab.com>
Approved-by: Dmitry Gruzd <dgruzd@gitlab.com>
Approved-by: Mireya Andres <mandres@gitlab.com>
Approved-by: Michael Lunøe <michael.lunoe@gmail.com>
Reviewed-by: Michael Lunøe <michael.lunoe@gmail.com>
Co-authored-by: Ross Byrne <robyrne@gitlab.com>