doc/flatpak-install: Make arg name consistent throughout
doc/flatpak-install: Make arg name consistent throughout

Closes: #2113
Approved by: matthiasclasen

flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak