This is not how the Miami Heat wanted to begin its six-game trip. Not only did the Heat start the long trip without three starters in Jimmy Butler (right big toe irritation), Kyle Lowry (personal reasons) and P.J. Tucker (left knee irritation). But the short-handed Heat (32-19) also couldn’t overcome the absence of three starters, as it fell to the Boston Celtics 122-92 on Monday night at TD Garden for its most lopsided loss of the season. Paired with Saturday’s triple-overtime loss to the Toronto Raptors, it marks the first time that Miami has dropped consecutive games since defeats on Jan. 2…