You cannot remove that package because, it doesn't contain "just" jetways, as the name might suggest. It also contains all ground vehicles that are used as Ground vehicle replacement, even when the Couatl engine is not running. But, since these same vehicles are also used by the full GSX, you can't remove them, even if you weren't interested in replacing the default Ground vehicles too.
So, while you might technically be able to use just the GSX World package alone ( but of course it won't be the "real" GSX, just a replacement set of default Ground Vehicles *and* Jetways ), you can't use GSX Pro without it.
This is also explained in the first pages of the manual, the chapter named "Two products in one: GSX Pro and GSX World", which explains what each package does.
