The 16-year-old boy who grounded a JetBlue flight with his bomb threat has completed his 80 hours of community service. As a result, he was reprimanded and discharged and warned not to behave like that again when he reappeared in the District “B” Boarded Hall Magistrates’ Court yesterday. Shiloh Cecil Bellott, of West 212 Street, New York, New York, had initially pleaded not guilty to the charge that while on …