DETROIT, Dec 23 (Reuters) - General Motors Co (GM.N) on Thursday joined a group of companies that will not send employees or top executives to the Consumer Electronics Show (CES) in Las Vegas next month due to the growing concerns about Omicron variant of the coronavirus. The U.S. automaker"s chief executive, Mary Barra, had been scheduled to give a keynote speech at the annual conference on Jan. 5, during which the company would have shown its electric Silverado pickup truck for the first time. Barra will still make the speech and presentation over the internet, a spokesman said.