Update sphinx requirement from ~=7.2.6 to ~=7.3.7

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/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v7.2.6...v7.3.7)

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

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

requirements_dev.txt

@@ -4,6 +4,6 @@ invoke
 coverage
 coveralls~=3.3.1
 rope~=1.7.0
-Sphinx~=7.2.6
+Sphinx~=7.3.7
 hfilesize~=0.1.0
 humanize~=4.9