TST: remove tests and docs for legacy (pre 0.12) hdf5 support
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Removing tests for old compatability because this issue is sufficiently old now, that people should be expected to have solved this themselves by now.

The first commit removes the legacy test for pandas v0.10. The second commit removes the legacy test for pandas v0.11.

This pull request replaces #17398. 

See also discussion in #17375.