Bump sphinx from 3.1.1 to 3.1.2

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.1.1 to 3.1.2.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v3.1.1...v3.1.2)

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

Author: dependabot-preview[bot]

setup.py

@@ -10,7 +10,7 @@
         "pre-commit~=2.4",
     ],
     "docs": [
-        "sphinx==3.1.1",
+        "sphinx==3.1.2",
         "sphinx-issues==1.2.0",
         "alabaster==0.7.12",
         "sphinx-version-warning==1.1.2",