Chris Johnson buys Jets’ No. 21 jersey from Ellis Lankster

Michael Vick isn’t the only new Jet picking a new number. Vick, who previously wore No. 7, originally said he’d wear No. 8 with the Jets, then changed his mind and picked No. 1. Now running back Chris Johnson has settled on No. 21. Johnson’s number in Tennessee, 28, is unavailable in New York: The…