MADISON, Wis. — Wisconsin Supreme Court Justice David Prosser announced Wednesday that he plans to retire this summer, ending nearly 18 years on the court marked by a rare physical altercation with a rival justice.Prosser, 73, said in a news release from the court that he would retire on July 31. The statement didn’t give a reason. In a letter to Gov. Scott Walker he said “the time has come to step down, pass the torch, and begin a new chapter in my life.”Prosser didn’t immediately respond to …