WASHINGTON — Former Proud Boys leader Enrique Tarrio and three other members of the far-right extremist group were convicted Thursday of a plot to attack the U.S. Capitol in a desperate bid to keep Donald Trump in power after the Republican lost the 2020 presidential election.A jury in Washington, D.C., found Tarrio guilty of seditious conspiracy after hearing from dozens of witnesses over more than three months in one of the most serious cases brought in the stunning attack that unfolded on Jan. 6, 2021, as the …