Palantir Technologies (PLTR 1.56%) shares have soared by 285% this year, while Nvidia (NVDA 2.15%) shares have advanced by 175%. Both companies play important roles in the burgeoning artificial intelligence (AI) economy, but several billionaire fund managers sold some of their Palantir stakes and bought more shares of Nvidia during the third quarter.Cliff Asness of AQR Capital Management sold 99,140 shares of Palantir, cutting his position by 16%. Meanwhile, he added 719,710 shares of Nvidia, upping his pos ...