DES MOINES — Iowa voters could get the chance to amend the state constitution with a requirement that any legislation seeking to change or repeal state income tax rates would need a two-thirds affirmative majority of both houses of the General Assembly to become law.Members of the Senate Ways and Means Committee, on an 11-5 party-line vote Wednesday, approved a resolution that would put the supermajority requirement on the ballot by 2022 if the measure is passed in exactly the same form by the current Legislature and the subsequent 89th General Assembly seated after next year’s election.“Iowans will have an opportunity to put a limitation on government spending,” said Sen.