Fix wrong downgrades of libgxps

[ManuelHu]

This should stop the extra "upgrade" of libgxps, as found in #115, #114 and olders.

[flathubbot]

Started test build 29056

[flathubbot]

Build 29056 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/11721/org.gnome.Evince.flatpakref

[hadess]

Would be great if you could document why this happens, either through a fixed issue, or flatpak-external-data-checker documentation.

[flathubbot]

Started test build 29063

[flathubbot]

Build 29063 failed

[ManuelHu]

Sorry @hadess , I was actually wrong (yes it is a bug in flatpak-external-data-checker, but this proposed fix does not fix it...) I have updated this PR to actually solve the issue.

The issue for f-e-d-c had been reported beforehand, and I added an explanation: https://github.com/flathub/flatpak-external-data-checker/issues/338

The problem is apparently, that old gnome releases were considered pre-release with an odd minor version number, a check that libgxps is hitting with their current version.

Edit: I think it should be safe to enable pre-releases at the moment as a short-time fix, as there are no pre-releases of libgxps

[flathubbot]

Started test build 29067

[flathubbot]

Build 29067 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/11731/org.gnome.Evince.flatpakref

[ManuelHu]

implemented in 06992cd