Upgrade packagecloud to 3.0.0
Packagecloud 3.0.0 was released this week. Changelog here: https://packagecloud.atlassian.net/wiki/spaces/ENTERPRISE/pages/15269920/Changelog
Which is a release we have been waiting on for a few months in order to offer CentOS/RHEL 8 packages to customers. gitlab-org/omnibus-gitlab#4479 (closed)
It would be awesome if we were able to get this in place for the 12.8 release.
cc\ @ljlane @ahanselka