Carl Icahn, the billionaire investor and adviser to President Donald Trump, said he’s betting on a decline in the market for renewable-fuel credits that he’s urging the president to overhaul. Icahn participates in the market through CVR Energy Inc., the oil refiner in which his Icahn Enterprises LP owns an 82 percent stake. CVR is required to buy the credits, known as renewable identification numbers, or RINs, when it makes gasoline. But Icahn said it’s delaying those purchases in a wager that prices will fall. In effect, he’s shorting the market. “I’m not selling ’em, I’m not buying ’em,” the...