Bump sphinx from 3.3.1 to 3.4.3 in /docs

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.3.1 to 3.4.3.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v3.3.1...v3.4.3)

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

Author: dependabot[bot]

{{cookiecutter.project_name}}/docs/requirements.txt

@@ -1,3 +1,3 @@
-sphinx==3.3.1
+sphinx==3.4.3
 sphinx-click==2.5.0
 sphinx-rtd-theme==0.5.0