DOC: fix small issues
read_clipboard passes the text to read_csv not read_table. See here for example: https://pandas.pydata.org/docs/dev/reference/api/pandas.read_clipboard.html

also replace "OS X" -> macOS

- [ ] 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
