* 10-year yield on pace for second straight daily decline * 20-year bond auction seen as mixed by analysts * Markets price 14.9% chance of 25-basis-point Fed hike, CME FedWatch shows (Updates to afternoon trading) NEW YORK, Oct 21 (Reuters) - US Treasury yields edged lower on Wednesday, as investors gauged the impact of higher interest rates on AI stocks that have helped propel economic growth, but eased from earlier lows after an auction of 20-year bonds.