Don't use deprecated ostree_repo_checkout_tree_at function
Don't use deprecated ostree_repo_checkout_tree_at function

We now use the new (almost identical) ostree_repo_checkout_at.

flatpak/flatpak,handsome-feng/flatpak,flatpak/flatpak,handsome-feng/flatpak,GeorgesStavracas/flatpak,matthiasclasen/flatpak,flatpak/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,GeorgesStavracas/flatpak,GeorgesStavracas/flatpak,GeorgesStavracas/flatpak,flatpak/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,GeorgesStavracas/flatpak,flatpak/flatpak,matthiasclasen/flatpak