libxml2 2.13.0 introduced some relevant changes regarding the treatment
of file paths on Windows[1]. Thus we un-xfail bug69753.phpt and its
companion, and we adjust dom004.phpt. And we also disable the
workaround for erroneous file:/ URIs on Windows.
[1] <https://gitlab.gnome.org/GNOME/libxml2/-/commit/8ab1b122c47bfced2b59f52351507ebc1eb50218>
Closes GH-16536.