Properly check for description presence for flac and vorbis.
Configure need to error out if there's no description, but isConfigSupported
should say true.
Differential Revision: https://phabricator.services.mozilla.com/D221656
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1917629
gecko-commit: a6af9793cee645db3af42b0078b73082b64cac17
gecko-reviewers: chunmin