`os.chdir` docstring is invalid rst

# Bug report

### Bug description:

```python
>>> from docutils.core import publish_doctree
>>> from posix import chdir
>>> publish_doctree(chdir.__doc__)
<string>:5: (ERROR/3) Unexpected indentation.
```


### CPython versions tested on:

CPython main branch

### Operating systems tested on:

Linux


### Linked PRs
* gh-136709
* gh-136719
* gh-136721