Change description:
Remove support for generating any <keygen> responses, always returning the default (empty) string

Changes to API surface:
HTML tags will continue to be processed as normal. However, all support for keytypes will be removed, as permitted by the HTML specification, resulting in the empty string being provided.

Links:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/pX5NbX0Xack/kmHsyMGJZAMJ (conclusion: https://groups.google.com/a/chromium.org/d/msg/blink-dev/pX5NbX0Xack/vHDX0041BAAJ )
Public standards discussion: https://github.com/whatwg/html/commit/1b438067d84da2ee95988842cdd8fe2655444936

Support in other browsers:
Internet Explorer: None
Firefox: Positive signals to remove ( https://groups.google.com/d/msg/mozilla.dev.platform/pAUG2VQ6xfQ/rjArKh6hMAAJ )
Safari: Unknown