chore(deps-dev): bump sphinx from 1.8.5 to 3.0.0

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 1.8.5 to 3.0.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v1.8.5...v3.0.0)

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

dev-requirements.txt

@@ -4,7 +4,7 @@ coveralls==2.0.0;python_version>='3.6'
 pytest==4.6.9;python_version<'3.0'
 pytest==5.4.1;python_version>='3.6'
 pytest-cov==2.6.1
-Sphinx==1.8.5
+Sphinx==3.0.0
 sphinx-bootstrap-theme==0.7.1
 sphinxcontrib-fulltoc==1.2.0
 sphinxcontrib-websupport==1.1.0