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>

requirements.txt

@@ -41,7 +41,7 @@ redis==3.5.3              # via -r requirements.in
 requests==2.23.0          # via sphinx
 six==1.11.0               # via more-itertools, packaging, pip-tools, python-dateutil
 snowballstemmer==2.0.0    # via sphinx
-sphinx==3.1.1             # via -r requirements.in
+sphinx==3.1.2             # via -r requirements.in
 sphinxcontrib-applehelp==1.0.2  # via sphinx
 sphinxcontrib-devhelp==1.0.2  # via sphinx
 sphinxcontrib-htmlhelp==1.0.3  # via sphinx