By Shrivathsa Sridhar PARIS (Reuters) -World number one Jannik Sinner flattened Jiri Lehecka into the French Open clay to make the fourth round but third seed Jessica Pegula had to dig her way out of trouble to beat 2019 runner-up Marketa Vondrousova on Saturday. As grey skies enveloped Roland Garros, Sinner gave Lehecka no respite to win the opening 11 games as fans checked their watches