Apple has settled with the U.S. Federal Trade Commission over in-app purchase disclosures, a new email from Apple CEO Tim Cook reveals. The email, posted by 9to5Mac, finds Cook explaining at length steps Apple has taken to make in-app purchases safer for customers with younger children. Cook also took issue with the FTC’s involvement. He wrote, “It doesn’t feel right for the FTC to sue over a case that had already been settled. To…