Add ^ to the path percent-encode set

[domenic]

Follow whatwg/url@9bc33c3.

Roll web platform tests to web-platform-tests/wpt@d86fcc9.

Depends on #291 happening first.

[domenic]

Implementation notes: this was trivial and I don't think AI would have helped. I could have tried to have AI one-shot it from the issue description, but it took 4 minutes total so it's doubtful that would actually save time.