style: Make CssUrl::is_fragment marginally more efficient.
style: Make CssUrl::is_fragment marginally more efficient.

No need to do utf8 shenanigans for what this function does.

Differential Revision: https://phabricator.services.mozilla.com/D97473

KiChjang/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo