open-uri: Use real filesystem path for OpenDirectory
open-uri: Use real filesystem path for OpenDirectory

Before this change the file manager would open inside the
document-portal directory like /run/user/1000/doc/10288756 which is not
very user-friendly. With this change it opens in the real filesystem
path. Now actions like "Show in Files" can be properly implemented.

flatpak/xdg-desktop-portal,flatpak/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,flatpak/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,flatpak/xdg-desktop-portal