A vehicle detonated in downtown Erbil on Wednesday, killing at least four people and injuring at least 29 – the first such attack to hit Iraq’s autonomous Kurdistan region in more than a year.Eyewitnesses to Wednesday’s attack said a Mercedes Benz pulled up to a checkpoint in front of the Erbil governorate building, near the ancient citadel at the center of the city, where the car was halted by guards. The bomb went off at 11:55 a.m.The attack could cause the Kurdistan Regional Governmen…