chore(deps): bump sphinx from 2.1.2 to 2.2.0

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 2.1.2 to 2.2.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES)
- [Commits](sphinx-doc/sphinx@v2.1.2...v2.2.0)

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

Author: dependabot-preview[bot]

requirements.txt

@@ -5,7 +5,7 @@ m2r~=0.2
 pep8~=1.7
 pycodestyle~=2.5
 -e git://github.com/pytest-dev/pytest-cov@master#egg=pytestcov
-Sphinx~=2.1
+Sphinx~=2.2
 sphinxcontrib-log-cabinet~=1.0
 sphinxcontrib-websupport~=1.1
 pip~=19.2