valid opaque-host string

valid opaque-host string

[1] Make IPv6 addresses in special URLs valid (annevk著, ) <https://github.com/whatwg/url/commit/aec942485630870e742d829dd9df61600796ad6e>

[2] Remove host parser's Unicode flag as it's unnecessary (annevk著, ) <https://github.com/whatwg/url/commit/af93f92a7b937ddacfaa7ce8c158a18a83c9c9d7>