It didn't say that you can't sell them, but that the clubs were equipped. It means that they are still your "chosen" clubs in your bag, so you would need to go to your equipment, and equip a different driver (or any club you want to sell), for eg the starter driver as if you are going to use it. The driver you want to use will no longer be "equipped" so you'll be able to sell it.
Hope this helps, and made sense. :-)
Good Luck!