Switch workers to Fedora to support newer macros

[lachmanfrantisek]

Since people started using new macros RPM functionalities that are not available (and probably won't be) on CentOS Stream 9, let's switch our workers to Fedora to help in this situation.

Long-term, we need to research how to provide matching environment: packit/research#219

[nforro]

Since people started using new macros that are not available (and probably won't be) on CentOS Stream 9, let's switch our workers to Fedora to help in this situation.

It's not about macros (that can be handled e.g. with mock or just by preparing a suitable environment for rpm), it's about new rpm features that won't be available in older/more stable distributions.

When we switch to rpm 4.20, spec files using %patchN syntax will become unparseable, however that shouldn't be a problem on Fedora where all packages have been mass-converted, though it could be an issue on CentOS Stream.