Roger Federer will not participate in the Tokyo Olympics, writing on social media Tuesday that he “experienced a setback” with his knee during the grass-court season. Federer had said before Wimbledon that he would make a decision about going to the Summer Games after the Grand Slam tournament ended. The 39-year-old from Switzerland lost in the quarterfinals at the All England Club last week to Hubert Hurkacz. Federer had two operations on his right knee in 2020 and went more than a full year between matches. He returned to Grand Slam action at the French Open and then pulled out of that tournament after three victories, saying he wanted to be rested and ready for the grass circuit—especially Wimbledon. On Tuesday, he said in a post on Twitter that because of the setback, he has “accepted that I must withdraw from the Tokyo Olympic Games. I am greatly disappointed, as …