By Tyler Clifford NEW YORK (Reuters) – WNBA star Brittney Griner and former U.S. Marine Paul Whelan, who are being held in Russia, could gain release by the end of this year, said former U.S. ambassador to the United Nations Bill Richardson, who traveled to Moscow in September. Richardson told CNN in an interview on Sunday that he had met with senior Russian officials and individuals close to Russian President Vladimir Putin during his trip, though his visit was not on behalf of the United States. “I am cautiously optimistic on the Griner (and) Whelan negotiations,” said Richardson, who is als…