(Reuters) -Joseph Vincent, a former informant for the U.S. Drug Enforcement Administration (DEA), on Tuesday became the fourth person to plead guilty in a U.S. court for his role in the 2021 assassination of Haiti's president that left a destabilizing power vacuum. A Haitian-American national, Vincent is among 11 defendants, including Colombian ex-soldiers and businessmen accused of helping supply funds and weapons and carrying out the nighttime attack at President Jovenel Moise's Port-au-Prince