Fixing 'names' doc for 'read_csv'
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I think there is a bug in the docs. This Jupyter notebook shows that the code does not work as expected from the docs https://gist.github.com/bessarabov/5e42bbb359fb86aaa87aed6c12a95bc9

So I've fixed the doc to match behaviour.
