SPRINGFIELD — Voters will have the opportunity to amend the state constitution on the 2020 ballot to take Illinois from a flat tax rate of 4.95% for individuals to a graduated one following the passage of Senate Joint Resolution Constitutional Amendment 1.The bill passed the House on a 73-44 party-line vote earlier in the week. Rep. Andre M. Thapedi, D-Chicago, did not vote.In order to propose the amendment to voters …