PHOENIX — Two more people have been arrested in the fatal beating of a teenage boy during a Halloween party last year in the Phoenix suburb of Queen Creek, authorities said Thursday.The number of suspects in the case is now six, including three juveniles, and there could be more arrests — including charging people who tampered with witnesses or obstructed the investigation, Queen Creek Police Chief Randy Brice said.“We’re not going to stop until we have everybody in custody,” Brice…