make it easier to support the Fedora job

The Fedora job is failing on a few things: https://gitlab.com/fdroid/fdroidserver/-/jobs/6714926952

The Fedora job is a lot harder to troubleshoot than the Debian-based jobs, and they are often quite bleeding edge. We can rely on the debian:testing job to test the bleeding edge, and it is a lot easier to troubleshoot. Currently, there is a change to either Python or an image processing lib (Pillow?) that now compresses PNGs differently than all previous releases. That breaks the tests based on processing images and checking the SHA-256 matches.

Here is a run with this merge request: https://gitlab.com/eighthave/fdroidserver/-/jobs/6751866075