SPRINGFIELD — Less than a month after winning a case that led to the U.S. Supreme Court decision that eliminates fair-share fees paid by nonmembers of public employee unions, Mark Janus is quitting his state job to work for the group that represented and funded his case.Janus, 65, currently serves as a child support specialist at the Illinois Department of Healthcare and Family Services.He announced Friday night that he will begin working as a senior fellow at the Illinois Policy Institute Aug. 1. The Illinois Policy …