Evaluate if we should adjust the copr repo priority in testing-farm

[kwk]

In #393 and #394 we've lowered the priority of the testing-farm-tag-repository. We might want to adjust the copr repo's priority instead.

[jchecahi]

@kwk While reviewing the testing farm logs of #390 I realized that TF runs of ppc64le and s390x are failing at prepare step because there's no testing-farm-tag-repository. I'll paste here the relevant part of the log, as those links are RedHat internal:

plan failed�[0m

The exception was caused by 1 earlier exceptions

Cause number 1:

    �[31mprepare step failed�[0m

    The exception was caused by 1 earlier exceptions

    Cause number 1:

        �[31mCommand '/var/ARTIFACTS/work-snapshot-gatingnbhkhfzl/tests/snapshot-gating/tree/tmt-prepare-wrapper.sh-default-1-default-0' returned 1.�[0m

        stdout (6 lines)
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        Copr repo for llvm-snapshots-incubator-20240408 402 kB/s | 138 kB     00:00    
        Copr copr.fedorainfracloud.org/@fedora-llvm-tea 1.3 MB/s | 441 kB     00:00    
        Package dnf-plugins-core-4.6.0-1.fc39.noarch is already installed.
        Dependencies resolved.
        Nothing to do.
        Complete!
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

        stderr (1 lines)
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        Error: No matching repo to modify: testing-farm-tag-repository.
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This seems to be consistent across all s390x and ppc64le runs.