Enable WebAudio APIs

Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1358149

Thorin had already found out that now the math of webaudio should be protected and opened mullvad-browser#224 (closed) for backporting. Then that issue was closed because we decided not to backport, but now that we have the patch we should investigate if we can enable some additional API without additional fingerprinting concerns.