RIO DE JANEIRO, Dec 23 (Reuters) - Brazilian state-run oil company Petrobras said on Thursday that it had been informed by Goldman Sachs (GS.N) that the U.S. bank and its subsidiaries now hold less than a 5% stake in the company. As a result, Petrobras said, Goldman Sachs "ceases to qualify as a holder of a relevant shareholding in the company"s capital stock."