The State Department denounced the Polish government for moving ahead with plans to try Solidarity union founder Lech Walesa for slander. Walesa faces the charges for saying that voter turnout in an Oct. 13 election was only 60%--not 79% as the government said. If convicted, Walesa, 42, winner of the 1983 Nobel Peace Prize, could be imprisoned for up to two years. State Department spokesman Bernard Kalb said, "We deplore the Polish government's reliance on repression . . . "