LONDON — For years, Labour didn’t want to talk about Brexit. It’s changed its mind. As the 10 th anniversary looms of Britain’s vote to the leave the European Union, senior ministers in the ruling center-left Labour Party are going studs up — daring to pin the U.K.’s sluggish economic performance on its departure from the trading bloc. “There is no doubting that the impact of Brexit is severe and long-lasting,” Chancellor Rachel Reeves said in an interview broadcast on Wednesday. “I’m glad that