MADISON, Wis. — A Wisconsin judge on Wednesday found probable cause to charge a police officer in the 2016 slaying of a Black man who was sitting in a parked car, taking the rare step of overruling prosecutors years after they declined to charge the officer.Milwaukee County Judge Glenn Yamahiro said probable cause existed to charge Joseph Mensah with homicide by negligent use of a weapon in Jay Anderson Jr.’s death. He will appoint a special prosecutor in 60 days, who will then determine whether to file charges.Yamahiro’s …