Drop the dep on preupgrade
Preupgrade is getting retired and is replaced by fedup in F18+. There is
still a soft dep on /usr/share/preupgrade/releases.list: PackageKit's
yum backend reads that file to decide if it should do distro upgrades.
However, that file as shipped in the preupgrade rpm is severely out of
date and isn't really useful any more in its current form.