It’s time to give the Washington Capitals some credit, as hard as that might be for the hockey diehards in these parts. The Bruins are not playing for their season Sunday simply because their scoring touch has grown moldy or because some of their best players have gone missing (see: Seguin, Tyler) since the curtain opened on the playoffs. Saturday afternoon at TD Garden was arguably the best game the Bruins have played in this series. For the first time, they got a power-play goal and a goal from one their six 20-goal scorers not named Chris Kelly, and it wasn’t even on the same tally.