Utilities stocks .GSPTTUT were top gainers, adding 0.6%, with alternative energy shares of companies such as Boralex BLX.TOrising 1.9%. By Shashwat Chauhan Dec 14 (Reuters) - Canada's main stock index slipped on Wednesday, as weakness in commodity-linked shares offset gains in utilities, while investors braced for another rate hike by the U.S. Federal Reserve. The Fed concludes its two-day policy meeting later on Wednesday, with traders betting that it would deliver a dialed-down 50-basis-point rate hike amid signs of cooling inflation.