Add focus-without-user-activation permissions policy

[siliu1]

MDN URL

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Permissions-Policy

What specific section or headline is this issue about?

No response

What information was incorrect, unhelpful, or incomplete?

w3c/webappsec-permissions-policy#273 (comment). Since the issue is resolved, we should add the new permissions policy entry to MDN web doc.

What did you expect to see?

add focus-without-user-activation permissions policy on https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Permissions-Policy.

Do you have any supporting links, references, or citations?

The spec update PR: whatwg/html#10672

Do you have anything more you want to share?

No response