SPRINGFIELD — Gov. Bruce Rauner is convinced his changes to a school-funding bill are legal.“I acted exactly as quickly, exactly as I laid out, exactly as my constitutional authority sets,” he told reporters today after announcing long-expected changes to a bill overhauling how the state doles out money to public schools.Rauner this morning recommended stripping about $215 million in Chicago teacher pension payments and $250 million in block funds for the city’s schools, among other things, from the …