lib/installation: Fix install/update_full() subpaths annotation
lib/installation: Fix install/update_full() subpaths annotation

Mark subpaths as a NULL terminated array. Without this the GIR makes
this a single utf8 parameter and bindings can't use it.

Closes: #1327
Approved by: cgwalters

handsome-feng/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,flatpak/flatpak