Fix TestXmlWriter
The output has changed since
https://cgit.kde.org/krita.git/commit/?id=bde1adee05bd82297570344af8bc39238d1ac2bb
or
https://cgit.kde.org/krita.git/commit/?id=79600d5811b8a4cb17823617d20260fde4296c98
and is presumably more correct now...