fixed formatting on to_csv() for categorical datetypes
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

Thanks @kyleolaughlin for the PR. what is the issue number this PR is addressing? This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. Thanks for contributing @kyleolaughlin, closing as stale for now, but please ping to reopen if you'd like to continue working on this.