COLUMBUS, Ohio — A downtown office building is worth its weight in gold, according to a federal judge who upheld a nearly century-old lease that tied rent to the current price of the metal.Last month’s ruling means rent paid by the company leasing the Commerce Building from a group of five property owners could jump from $6,000 annually to more than $300,000.At issue is a so-called “gold clause” included in the original 1919 lease. The provision, common at the time, linked rent to the price of gold …