Shares of Uber retreated Wednesday as the leading U.S. indexes finished the day mixed. Michael Nagle / Bloomberg via Getty Images Close Key Takeaways A big mobility and food-delivery player came under pressure after a competitor announced an expansion of its robotaxi partnership, while a cloud-based business software provider soared after an activist investment firm announced a stake. The S&P 500 ended Wednesday with a loss of about 0.1% as the Federal Reserve announced a widely expected quarter-percentage- ...