Fix typo for ANSIBLE_FORCE_COLOR in Changelog

In https://github.com/ansible/ansible/blob/devel/lib/ansible/color.py it is:

```PYTHON
if os.getenv("ANSIBLE_FORCE_COLOR") is not None:
        ANSIBLE_COLOR=True
```
In the Changelog it's `ANSIBLE_FORCECOLOR=1`
This feature is not documented elsewhere, and I spent 10 minutes figuring out why it's not working.

Maybe it can help someone else too.