An arbitrator ruled yesterday that Michael Vick must repay $20 million dollars in bonuses to the Atlanta Falcons for violating his $130 million contract. Stephen Burbank, the University of Pennsylvania law professor who presided over last week's arbitration hearing, agreed with the Falcons that Vick violated his contract when he admitted his role in a dogfighting ring. The team also argued that Vick used proceeds from his contract to bankroll the illegal operation.