By Sarah N. Lynch WASHINGTON (Reuters) -Enrique Tarrio, the former top leader of the right-wing group the Proud Boys, pleaded not guilty on Tuesday to criminal charges accusing him of conspiring to block Congress from certifying President Joe Biden’s 2020 election victory ahead of last year’s attack on the U.S. Capitol. Tarrio’s attorney entered the not guilty plea on his behalf during a virtual hearing in the U.S. District Court for the District of Columbia. The judge also announced a postponement in the planned May 18 start to the trial. Tarrio, 38, is one of the most high-profile of the mor…