Previously, Initial Setup would arrange for Tour to be launched at the
end of the setup process, unless disabled in the vendor configuration
file.

In GNOME 40, users will launch the tour themselves, either from a
[welcome dialogue shown by the shell itself][0] or from [the tour's app
launcher][1].

Remove all logic related to launching the tour.

[0]: https://gitlab.gnome.org/Teams/Design/os-mockups/-/issues/90
[1]: https://gitlab.gnome.org/GNOME/gnome-tour/-/issues/28

Part-of: <https://gitlab.gnome.org/GNOME/gnome-initial-setup/-/merge_requests/111>