The head of Tesla’s controversial “Autopilot” program said Wednesday he was quitting the company, weeks after news broke of an expanded federal probe into the driver-assistance feature’s safety. “It’s been a great pleasure to help Tesla towards its goals over the last 5 years and a difficult decision to part ways,” Andrej Karpathy tweeted Wednesday afternoon. “In that time, Autopilot graduated from lane keeping to city streets and I look forward to seeing the exceptionally strong Autopilot team continue that momentum.” Tesla CEO Elon Musk responded almost immediately on Twitter, saying “Thanks…