Toby Melville/ReutersWikiLeaks founder Julian Assange on Tuesday did not attend the opening of what may be his final U.K. legal effort to stop his extradition to the U.S. to face spying charges, with his lawyer saying he was unable to attend for health reasons.The two-day hearing at London’s High Court is set to determine if Assange, 52, can be granted a new appeal hearing against a 2022 decision by the British government that he can be lawfully extradited to the U.S. to answer 18 criminal charg