Paul Vallas and Brandon Johnson will meet in a runoff to be the next mayor of Chicago after voters on Tuesday denied incumbent Lori Lightfoot a second term, issuing a rebuke to a leader who made history as head of the nation’s third-largest city.Vallas, a former schools CEO backed by the police union, and Johnson, a Cook County commissioner endorsed by the Chicago Teachers Union, advanced to the April 4 runoff after none of the nine candidates was able to secure over 50% of the vote to win outright.Lightfoot, the …