The Maine Turnpike Authority has postponed voting on a plan to increase tolls on the 109-mile highway. At its regular meeting Thursday at the authority’s Portland headquarters, board members voted to defer a vote until August. Under the authority’s initial proposal, rolled out in early June, turnpike officials were seeking a 26 percent toll increase to raise an additional $26 million a year to cover the turnpike’s operating budget, maintenance, and long-term debt service. The board came up with a plan Thursday that would delay some of the turnpike’s major capital projects so that the necessary toll increases would amount to $21 million to $22 million a year, not $26 million.