Remove dead code
Delete the old-and-still-unused metadata code.
Closes https://gitlab.gnome.org/GNOME/gnome-games/issues/113, https://gitlab.gnome.org/GNOME/gnome-games/issues/115
Delete the old-and-still-unused metadata code.
Closes https://gitlab.gnome.org/GNOME/gnome-games/issues/113, https://gitlab.gnome.org/GNOME/gnome-games/issues/115