By a single vote, the Senate gave final approval on Thursday to a measure to block cities and counties from organizing retirement savings accounts for workers who have no access to employer-sponsored plans. The vote reverses a Labor Department rule that allows local governments to automatically enroll private-sector workers in retirement plans unless they opt out.Under the law that governs pensions, employers must show that they are managing their retirement programs on behalf of their workers, not the investment funds — a provision some Republicans argued that state and city plans could skirt.“This is a problem that could be just as easily dealt with at the federal level. But it’s not being dealt with. Rather than doing nothing, states are stepping in and recognizing that it’s in their financial interests to act and build these systems,”