Enable `crb` and `epel` for centos-stream testing

[psss]

These are necessary so that Fedora CI pull requests against epel9 are working. Related links:

• https://issues.redhat.com/browse/OSCI-6783
• https://src.fedoraproject.org/rpms/tmt/pull-request/142

[lukaszachy]

But this will enable crb and epel for all centos-stream jobs, not just those against epel9 target, won't it?

[msrb]

Lukas is right, let's try here: https://github.com/fedora-ci/installability-pipeline/pull/41