By Gabrielle Tétrault-Farber, Iain Axon and Karolos Grohmann BEIJING (Reuters) -Russia’s 15-year-old figure skating sensation Kamila Valieva giggled with her coaches but turned serious for her own routine as she practiced on Thursday at the Winter Olympics despite reports of testing positive for a banned substance. The teenager was part of the Russian Olympic Committee (ROC) team that won the figure skating team event https://www.reuters.com/lifestyle/sports/figureskating-russians-widen-lead-team-event-quest-2nd-medal-2022-02-07 on Monday, ahead of the United States and Japan. But their medal …