SAN ANTONIO, Texas – At least for one night, RJ Barrett and the Knicks got their groove back. New York set the nets ablaze Tuesday against the Spurs, burying 18 of its 38 3-pointers in an emphatic 121-109 victory. It snapped a three-game losing streak and represented the Knicks’ first win in San Antonio in nearly eight years. Barrett, who had been mired in a deep shooting slump, scored 32 points while knocking down 7 of his 8 treys. It was his highest point total since October, occurring just three days after coach Tom Thibodeau said Barrett needs to recover his work ethic from last season by …