WAUKESHA, Wis.—Four of the six people killed by an SUV racing through a Wisconsin Christmas parade on Sunday were affiliated with the Milwaukee Dancing Grannies, a beloved pompom-thrusting dance troupe, according to a local newspaper. Ginny Sorenson, 79, LeAnna Owen, 71, and Tamara Durand, 52, were members, while Wilhelm Hospel, 81, helped the group, according…