The parent company of Assurant Health said Tuesday that it will sell or shut down the Milwaukee health insurer — which employs 1,200 people in the area — by the end of next year. Assurant Health has struggled to adjust to changes in the health insurance market imposed by the Affordable Care Act and is expected to report an operating loss of $80 million to $90 million in its first quarter. That comes after it lost $64 million last year. The company, whose headquarters is in downtown Milwaukee, specializes in health insurance for small employers and individuals, the two market...