Update sphinx requirement from <=3.0.3,>=1.8.1 to >=1.8.1,<4.3.3 (#654)

Updates the requirements on [sphinx](https://github.com/sphinx-doc/sphinx) to permit the latest version.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v1.8.1...v4.3.2)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-type: direct:development
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements-dev.txt

@@ -5,7 +5,7 @@ pytest==6.2.5
 pytest-cov==3.0.0
 pytest-sugar==0.9.4
 PyMySQL>=0.9,<=0.9.3
-sphinx>=1.8.1, <=3.0.3
+sphinx>=1.8.1, <4.3.3
 sphinxcontrib-asyncio==0.3.0
 sqlalchemy>1.2.12,<=1.3.16
 uvloop==0.16.0