NEW YORK — Dollar Tree said Friday that it has agreed to sell 330 of its stores to the private equity firm Sycamore Partners in order to get regulatory approval for its $8.5 billion purchase of Family Dollar. The Chesapeake, Virginia-based company said earlier this month that it would sell the stores, but it had not disclosed the buyer. It didn’t say how much Sycamore Partners will pay for the stores, which bring in about $500 million in annual revenue. It also didn’t disclose which stores are being sold....