Bump sphinx from 2.2.2 to 2.3.0

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 2.2.2 to 2.3.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES)
- [Commits](sphinx-doc/sphinx@v2.2.2...v2.3.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

setup.py

@@ -10,7 +10,7 @@
         "pre-commit~=1.20",
     ],
     "docs": [
-        "sphinx==2.2.2",
+        "sphinx==2.3.0",
         "sphinx-issues==1.2.0",
         "alabaster==0.7.12",
         "sphinx-version-warning==1.1.2",