BOSTON (AP) — The Celtics appeared to be skipping toward the second round of the NBA playoffs following a 32-point road win in Game 4 at Philadelphia. But back-to-back convincing wins by the 76ers in Game 5 and Game 6 have left a Boston team that once looked like a favorite to emerge from the Eastern Conference on the brink of an epic collapse. A loss in Saturday’s Game 7 would be the No. 2 seed Celtics’ earliest exit from the playoffs since the 2020-21 season. They may have to do it with star