Building based on CentOS 8 no longer works, because it is EOL.
- Group Reviewers
- rHGaeeb54261099: packaging: replace centos8 by rockylinux 8
We'll need to rename some additional things like the build targets as well then (make docker-centos8). Perhaps it would be better to have a follow-up where we instead rename to 'rhel8', then we cover all variants.