astropy v7.0: some removed functionality is used in tests

[pllim]

According to astropy-integration-testing run, there is failure with stable version but not dev, so this package needs a new release to be compatible with astropy v7.0.0 (but only if you want the affected test to pass, not change to package functionality). FYI.

[bsipocz]

The failures are in the tests/testing imports, and none of the actual astroquery functionalities are affected.

And I really do not appreciate that such an out of deprecation cycle API change would force us to release here; especially to make it happen urgently, so would rather just pass the ball back and would like to ask the revert of this PR from the 7.0 release in favour of doing it properly, with a deprecation at first, after all these functions were explicitly part of the API and were listed in __all__, too.