I get it, you sold it (congratulations) and you want to cut the ties. Well, I have three suggestions. The first is to contact the buyer. If you are still in touch with them, this is always the easiest. Second, check the WHOIS (who.godaddy.com) and see if they changed any of the contact data elements, as that would allow you to reach out to the newly listed party. Finally, you can always report an Invalid Whois via a link on the WHOIS record itself (after you enter the domain name).
I hope that helps,
Thomas D. - GoDaddy | Community Moderator 24/7 support available at x.co/247support