MIAMI – The shot wasn’t in the air for more than a few seconds, but for the collection of green-clad players watching, it felt like an eternity. For three quarters the Celtics had fended off a relentless, never-ending Heat charge, battling as a 15-point first quarter lead was whittled to six at the end of the second, and as a 12-point edge with 3 ½ minutes to play was sliced to two. Now there they were, 17 seconds on the clock, up two, a trip to the Finals on the line and Jimmy Butler, the latest villain in Boston’s long history of them, was pulling up from three.