The Los Angeles Lakers are doing their best to forget all those awful memories of playing in the Boston Garden. Kobe Bryant sank the go-ahead basket with 7.3 seconds left, and the Lakers won 90-89 on Sunday for their third consecutive victory over the struggling Celtics. Boston has not been able to make good on the traditional "Beat L.A.!" chant since winning 131-92 to clinch the 2008 NBA…