Fix Type Annotations in pandas/_config/config.py
Part of #25882

Current errors are as follows:

```sh
pandas/_config/config.py:60: error: Need type annotation for '_deprecated_options'
pandas/_config/config.py:61: error: Need type annotation for '_registered_options'
pandas/_config/config.py:62: error: Need type annotation for '_global_config'
```

Should add annotations and remove this module from mypy.ini - think this is straightforward so community PR is certainly welcome!