Bump furo from 2020.12.9b21 to 2020.12.30b24 in /docs (#216)

Bumps [furo](https://github.com/pradyunsg/furo) from 2020.12.9b21 to 2020.12.30b24.
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](pradyunsg/furo@2020.12.09.beta21...2020.12.30.beta24)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/requirements.txt

@@ -1,2 +1,2 @@
 sphinx==3.4.3
-furo==2020.12.9b21
+furo==2020.12.30b24