PHILADELPHIA — The Boston Celtics and Philadelphia 76ers are heading to a Game 7 in their first round series after another convincing Sixers win, 106-93 . The Celtics offense was stagnant once again, leaving the Celtics looking slow and confused. The Celtics offense scored less than 100 points nine times this season, or about 11% of the time. They've now done it in three of their six games against the Sixers, squandering an opportunity to get rest ahead of the second round and now fighting for the chance to even advance.  Box Score Game Flow The Sixers came out to an 11-4 run, not because they dominated or anything, but because Boston missed more shots than Philly did. They missed layups and turned the ball over, but settled down by the 6:24 mark to cut it to three. That grew to a 10-2 run to take the lead.…