Billionaire Edward Lampert and his hedge fund, RBS Partners, have cut their stake in AutoNation, one of South Florida’s biggest public companies, Bloomberg reported. Lampert and RBS once owned more than half of Fort Lauderdale-based AutoNation (NYSE: AN) but now owns significantly less than half. Bloomberg said the fund reported to the U.S. Securities and Exchange Commission on Thursday that its stake in AutoNation was 34.6 million shares, valued at about $1.37 billion as of Dec. 31. Lampert…