Billionaire Warren Buffett slashed Berkshire Hathaway’s massive Apple stake in a move that could prove unsettling for the broader stock market because the investor is so revered and there had been little positive financial news lately. The Apple sale is such a surprise because just two years ago Buffett was calling the stock one of the four giants of his conglomerate’s business alongside Berkshire insurance, utility and BNSF railroad businesses that it owns outright. That gave investors the impression that Buffett might hold onto Apple indefinitely like he has with the Coca-Cola and American Express shares he bought decades ago although he has trimmed the Apple stake over the past year.