Fix test skipping, get rid of libtbx.approx_equal
Fix test skipping, get rid of libtbx.approx_equal

1. '''print("Skip"); return''' shows as a passed test in pytest,
   as it should. If you want to skip a test then you can use one
   of the methods described at
   https://docs.pytest.org/en/latest/skipping.html

2. There is no need to depend on libtbx for fuzzy comparison, cf.
   https://docs.pytest.org/en/latest/builtin.html#pytest.approx

3. Rename the test slightly. I like helpfully verbose test names.

dials/dials,dials/dials,dials/dials,dials/dials,dials/dials