RICHMOND, Va. — When Sigal Chattah goes to federal court to challenge a school mask mandate issued by the governor of Nevada, she’ll likely be required to wear the very thing she’s arguing against: a mask.That’s because U.S. District Court in Las Vegas and other courts where plaintiffs are demanding their freedoms from masking and COVID-19 vaccinations require everyone to wear masks. Just as in-person hearings and trials resumed at courthouses around the country, a surge of coronavirus cases sparked by the delta variant …