Update sphinx requirement from <4.4.1,>=1.8.1 to 4.5.0 (#751)

Updates the requirements on [Sphinx](https://github.com/sphinx-doc/sphinx) to 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...v4.5.0)

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

Co-authored-by: Richard Schwab <[email protected]>

Author: dependabot[bot]

requirements-dev.txt

@@ -5,7 +5,7 @@ pytest==7.1.1
 pytest-cov==3.0.0
 pytest-sugar==0.9.4
 PyMySQL==1.0.2
-sphinx>=1.8.1, <4.4.1
+sphinx>=1.8.1, <4.5.1
 sphinxcontrib-asyncio==0.3.0
 SQLAlchemy==1.3.24
 uvloop==0.16.0; python_version < '3.11'