The test file was taken from acid3, which does actually serve documents
for those locations.
For us, those documents never were available (as we're using `setHtml`
which uses a `data` URL internally), but the test does work just fine
without them. It was intended to test `appendChild` with different tags,
see the original commit (6c241f96ed) as
well as #2723 for details.
So far, them being there wasn't a problem, but with Qt 5.15.2 (or rather
the underlying Chromium 83), we get errors logged like this one:
"Invalid relative frame source URL (xhtml.3) within data URL.", source: (47)
So let's just not set them at all.
See #5752.
Florian Bruhin
Jay Kamat