x11/xdg-user-dirs-gtk: update to 0.16

Changelog: https://gitlab.gnome.org/GNOME/xdg-user-dirs-gtk/-/blob/0.16/NEWS

Note that the new systemd service has been patched out.

PR: 291660
(cherry picked from commit 1aaf5bdb0a4f3f3aa1f5e52cbee6e2bdeb15352c)