Remove errant comma from viewer_audio.css
Remove errant comma from viewer_audio.css

readium/readium-js-viewer,AndyHubert/readium-js-viewer,GermanCentralLibraryForTheBlind/readium-js-viewer,GermanCentralLibraryForTheBlind/readium-js-viewer,AndyHubert/readium-js-viewer,readium/readium-js-viewer