Kevin Costner reportedly demanded a “script approval” in order to return to the final season of Yellowstone — but Paramount Network refused to concede to the actor’s ultimatum, RadarOnline.com has learned. On Thursday, Costner, 69, finally admitted to fans of the western series that he would not be returning as modern cowboy John Dutton after months of bitter negotiations between the actor and studio. Despite an ongoing feud between Costner and Yellowstone creator Taylor Sheridan, Paramount attempted to wrangle the actor back for the final season. The studio reportedly made the actor several o…