Autotests: adapt test data to Qt no longer emitting ":" before base attribute

In older Qt versions QDomElement has been streaming itself to QTextStream with the "base" attribute name prefixed by ":".

Qt 6.5.1 at least no longer does that, so in the test reference data update the strings and respectively affected hash values.

See ElementWrapper::childNodesAsXML(const QDomElement &) for the code affected by the change and yielding a different string.

I could not find a respective entry in the Qt release notes or a bugreport, just noticed this test started to fail now, both with newer MRs against Qt 6.5 (CI seems to have passed still with Qt 6.4) and locally.