The Panthers needed a defenseman to provide some offense to advance to the Eastern Conference finals. Gustav Forsling provided the game-winning goal with 1:33 left in the third period to put Florida ahead of Boston in a 2-1 victory in the TD Garden, clinching the series in Game 6 Friday night. After three blowouts in the first three games of the Bruins’ and Panthers’ second-round series, the margin between the two teams narrowed.