27820 clarify that read parquet accepts a directory path
- [x] closes #27820 
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @HawkinsBA! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-12-05 07:53:07 UTC I saw in the previous pull request for this issue that an example might be helpful. Is that still needed with these changes, and if so what would be the best way of going about that? sure