CLN: spelling fixes in docstrings
- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Appears that `TestHDFStore.test_append_with_data_columns` is failing in 1 of the 5 TravisCI builds. 

I didn't change that function, and it looks to have passed in all other Azure pipeline builds. Is this a known flaky test? > Is this a known flaky test?

yes. Thanks @akosfurton! The failing Travis build was unrelated test failure