Tracy Morgan relentlessly heckled Jeremy Lin upon his return to MSG with the Houston Rockets. “Tracy was yelling, ‘Hey, Jeremy! How about the Knicks? Best record in the East!’ ” a spy told us. The “30 Rock” star also gave Rocket James Harden a ribbing: “I used to have a mohawk my uncle gave me, just like James Harden . . . But mine was crooked.” When Morgan spotted Kate Upton in the crowd, he razzed Lin, “Why are you flirting with Kate? She’s not even looking at you!” Also there: 50 Cent.