tests: We need to update repo with flatpak build-update-repo, not just ostree summary -U
tests: We need to update repo with flatpak build-update-repo, not just ostree summary -U

If not, there will not be the flatpak cache in the summary and we'll create a g_warning that
aborts the tests.

matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak