[webkit-dev] Disabling keygen element by default

Hi all, HTML keygen element had been removed from Chrome since 2017, and Firefox recently removed it in Firefox 69: https://bugzilla.mozilla.org/show_bug.cgi?id=1315460 I've put a patch up to disable keygen element by default on https://bugs.webkit.org/show_bug.cgi?id=200850. - R. Niwa