Roger Federer announced Thursday morning that he is retiring from singles tennis competition after 24 years on the ATP Tour. The Laver Cup in London next week, beginning on Sept. 23, will be his final professional appearance. In an audio clip posted on social media, Federer cited age-related limitations for his decision to retire. The 20-time Grand Slam winner has suffered several injuries in recent years, some of which have required surgery. “I am 41 years old. I’ve played more than 1,500 matches over 24 years,” Federer said. “Tennis has treated me more generously than I ever would have dream…