WASHINGTON — The justices of the U.S. Supreme Court have their first chance this week to decide whether they have the appetite for another major fight over President Barack Obama’s health-care law. Some of the same players who mounted the first failed effort to kill the law altogether now want the justices to rule that subsidies that help millions of low- and middle-income people afford their premiums under the law are illegal. The challengers are appealing a unanimous ruling of a three-judge panel of …