Add new merge trains link

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/160757



Merged-by: Terri Chu <tchu@gitlab.com>
Approved-by: Veethika Mishra <6115425-veethika@users.noreply.gitlab.com>
Approved-by: Serhii Yarynovskyi <syarynovskyi@gitlab.com>
Approved-by: Ammar Alakkad <aalakkad@gitlab.com>
Approved-by: Artur Fedorov <afedorov@gitlab.com>
Approved-by: Terri Chu <tchu@gitlab.com>
Reviewed-by: Terri Chu <tchu@gitlab.com>
Reviewed-by: Veethika Mishra <6115425-veethika@users.noreply.gitlab.com>
Reviewed-by: Artur Fedorov <afedorov@gitlab.com>
Co-authored-by: Payton Burdette <pburdette@gitlab.com>