Upgrade sidekiq-cron to v1.8.0

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/100124



Merged-by: Sean McGivern <sean@gitlab.com>
Approved-by: Alejandro Rodríguez <alejandro@gitlab.com>
Approved-by: Sean McGivern <sean@gitlab.com>
Co-authored-by: Heinrich Lee Yu <heinrich@gitlab.com>