gnome-packagekit external deps

[Richard Hughes <hughsient gmail com>]

To fix some bugs, I've raised the gnome-packagekit dep on PackageKit
to 0.5.5. I'm asking for retrospective permission to do so as I've
been poked by a couple of people now.

PackageKit 0.5.5 was released yesterday, and is part of the
PACKAGEKIT_0_5_x series. Distros should have no real reason not to
upgrade, and because 0.5.5 fixes a large number of bugs compared to
0.5.4, i would recommend it.

Okay for me to update the external deps wiki?

Thanks (and sorry for not asking first...),

Richard.