CI/DOC: warning in docbuild
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [ ] whatsnew entry

merge in green ```
----> 1 pd.read_csv(io.StringIO(data), true_values=["Yes"], false_values=["No"])

TypeError: initial_value must be str or None, not DataFrame
```

Maybe we need to freeze the old example so it doesnt get evaluated?  i dont know how that works use a ioython block and paste the example in Thx for fixing @jreback green but im really not confident when it comes to code-block stuff don't need the okwarning but ok