Bump furo from 2020.12.30b24 to 2021.4.11b34

Bumps [furo](https://github.com/pradyunsg/furo) from 2020.12.30b24 to 2021.4.11b34.
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](pradyunsg/furo@2020.12.30.beta24...2021.04.11.beta34)

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

setup.cfg

@@ -38,15 +38,15 @@ dev =
     flake8-absolute-import>=1.0
     flake8-implicit-str-concat==0.2.0
     flake8-print==4.0.0
-    furo==2020.12.30b24
+    furo==2021.4.11b34
     isort==5.7.0
     pre-commit==2.10.0
     pytest==6.2.2
     pytest-cov==2.11.1
     yamllint==1.26.0
 doc =
     Sphinx==3.4.3
-    furo==2020.12.30b24
+    furo==2021.4.11b34
 lint =
     black==20.8b1
     flake8==3.8.4