Fix compiler warnings
Fix compiler warnings

There are a number of -Wshadow warnings in document-portal/.
Fix them.

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