DOC: Rolling.apply states incorrect default for raw argument
### 

- [X] I have checked that the issue still exists on the latest versions of the docs on `master` [here](https://pandas.pydata.org/docs/dev/)


### Location of the documentation

https://pandas.pydata.org/docs/reference/api/pandas.core.window.rolling.Rolling.apply.html

### Documentation problem

The parameters description for `raw` states the default is `None`, while the default is actually `False`.

### Suggested fix for documentation

Update the default to `False`.