task-gnome-desktop: recommend gnome-initial-setup

gnome-initial-setup is already included in live images, as live-task-gnome recommends task-telugu-gnome-desktop, that recommends gnome-initial-setup. Not including the initial setup in the installed system seems inconsistent.

I'm posting this patch here and tagging @jbicha as it seems that the message on the pkg-gnome-maintainers list went unnoticed. Sorry for the ping, but as the freeze is nearing I'd really prefer to have this included in the next Debian release, as not being greeted by the initial GNOME tour on a fresh system always feels odd.

Closes: #1006486