WASHINGTON — The Supreme Court on Monday said it won’t take up a case that asked it to decide whether it’s sex discrimination for the government to require only men to register for the draft when they turn 18.In a statement, three justices said Congress is weighing whether to change the Military Selective Service Act, which requires men but not women to register for the draft. They said that was a reason for the court not to take the case.“It remains to be seen, of course, whether Congress will end gender-based …