LONDON — Britain’s Labour Party has upped its attacks in the pivotal Makerfield by-election. But its candidate, Andy Burnham, is still playing nice. In the tight June 18 fight for the Greater Manchester seat, Burnham — who is making a dual pitch to be the local MP as well as a potential replacement for Labour’s own prime minister Keir Starmer — has been largely making an upbeat case to voters and insisting he is “just gonna talk about what I’m going to do.” That’s in stark contrast to a central