lib: Fix declaration of xdg_app_installed_ref_load_metadata
lib: Fix declaration of xdg_app_installed_ref_load_metadata

We changed this to not be const

matthiasclasen/xdg-app,matthiasclasen/xdg-app,matthiasclasen/flatpak,handsome-feng/flatpak,alexlarsson/xdg-app,amigadave/flatpak,GeorgesStavracas/flatpak,matthiasclasen/flatpak,GeorgesStavracas/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,amigadave/flatpak,matthiasclasen/xdg-app,matthiasclasen/flatpak,GeorgesStavracas/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,alexlarsson/xdg-app,flatpak/flatpak,GeorgesStavracas/flatpak,alexlarsson/xdg-app,matthiasclasen/xdg-app,GeorgesStavracas/flatpak,amigadave/flatpak,flatpak/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,flatpak/flatpak,handsome-feng/flatpak,alexlarsson/xdg-app,amigadave/flatpak