Lydia Hearst is leaving the city. We hear the fashion model and publishing heiress — the daughter of famed 1970s kidnap victim Patty Hearst Shaw — is moving to Los Angeles to pursue an acting career full time. She’s already had a guest spot on “Gossip Girl” and posed nude for Playboy. “She’s going out for pilot season,” a source tells us. Making the trek with Hearst is her new boyfriend, singer Ryan Cabrera.