Update dependency Sphinx to v4 (#105)

renovate[bot] · renovate-bot · web-flow · commit 8e68b0aeabf7 · 2021-06-28T08:03:40.000+01:00
Co-authored-by: Renovate Bot &lt;bot@renovateapp.com&gt;
diff --git a/requirements_dev.txt b/requirements_dev.txt
@@ -3,7 +3,7 @@ coverage==5.5
 flake8==3.9.2
 pip==21.1.3
 pytest==6.2.4
-Sphinx==3.5.4
+Sphinx==4.0.2
 tox==3.23.1
 twine==3.4.1
 wheel==0.36.2
