Reported by Anne van Kesteren in https://bugs.webkit.org/show_bug.cgi?id=228122#c42:
> removeQueryParameters looks buggy as instead of using a serializer for
> the resulting query you append the raw keys and values to a string. Meaning
> that %3D would become = and %26 becomes &, etc. unless I'm missing
> something. You probably want to use the internal equivalent of
> URLSearchParams instead.