The Heat’s best shooter isn’t shooting enough. Most nights, it’s not a problem. After all, Chris Bosh might be the team’s most reliable offensive option, but he’s on a team with Dwyane Wade and LeBron James, two of the best scorers in the NBA. But then there are times like Sunday and the Heat’s 100-98 loss to the Celtics. In a game that Heat coach Erik Spoelstra called one of his team’s most inefficient of the season, Bosh attempted just three shots in the second half and overtime periods. It was as if James, Wade and Ray Allen completely forgot that Bosh, whose 54.3 percent field-goal shooting leads the Heat, was on the floor.