DOC: skip evaluation of code in v0.8.0 release notes
As noted in https://github.com/pandas-dev/pandas/pull/39364#issuecomment-778678278. A little unclear to me why it's not failing in other pull requests, as I can reproduce the issue locally.

- [ ] ~~closes #xxxx~~
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] ~~whatsnew entry~~
