By Tzvi Machlin The Detroit Lions take on the Dallas Cowboys this Sunday in a game that will likely eliminate the loser from contention for the top seed in the NFC. But the Lions will be a bit short-handed in their secondary for the game. According to NFL insider Ian Rapoport, Lions starting safety CJ Gardner-Johnson has already been ruled out of the game. Gardner-Johnson is still recovering from a torn pectoral injury and has not played since September. However, Gardner-Johnson recently had his practice window opened, so there is optimism that he will at least be back for the Lions in time fo…