[Ci-users] CentOS CI infra changes: retiring ci.centos.org legacy jenkins

as a FYI message : the legacy Jenkins server (initially shared instance between CI tenants) and available behind https://ci.centos.org will be decommissioned and powered off next week.

It's not used anymore and was just put online with a notification about shutting it down and pointing to relevant ticket template to ask to be migrated to openshift (2 years ago)

As we're also decommissioning other part of the CI infra, we'll also just delete that one from and also remove A record from public DNS (actually pointing to haproxy in front)

related ticket: https://pagure.io/centos-infra/issue/931

Kind Regards