x11/xdg-desktop-portal-luminous: update to 0.1.6

Changes: https://github.com/waycrate/xdg-desktop-portal-luminous/releases/tag/v0.1.5
Changes: https://github.com/waycrate/xdg-desktop-portal-luminous/releases/tag/v0.1.6
Reported by: GitHub (watch releases)