When I try to uninstall my managed package, it tells me that I can't because my custom object, Carrier, is referenced by a lookup field on Account. So I went to Account and deleted the lookup field. Now it's saying that I can't uninstall my package because the custom object Carrier is referenced by my deleted lookup field. (The lookup field now has "_del" appended to the end of the name to indicate that it has been deleted. I see an option to undelete it but no option to permanently delete it.) What do I do?