CI: On CentOS Stream, use EPEL Next, not EPEL proper
    
    Also, make sure to never pull from EPEL's Koji repo,
    as is also exposes RHEL packages in the metadata, but they error 403.
    
        [MIRROR] libgcrypt-1.10.0-4.el9_0.x86_64.rpm: Status code: 403 for https://infrastructure.fedoraproject.org/repo/rhel/rhel9/x86_64/rhel-9-for-x86_64-baseos-rpms/Packages/l/libgcrypt-1.10.0-4.el9_0.x86_64.rpm
    
    We just pull from the CentOS Stream Koji repo and EPEL Next Koji repo.
    See the mock config for centos-stream+epel-next-9.