CI/TST: temporary xfail spam url tests
xref https://github.com/pandas-dev/pandas/issues/28708
This temporary xfails the tests to get CI green again. 

But, since the web page listing the html pages is gone, we can maybe also just remove the test? (I don't know if it was testing something specifically, that we might need to replace with another test, though) @jorisvandenbossche Hopefully #28710 should pass (passes locally) and this won't be necessary. Yes, also just saw that, perfect!