Update sphinx requirement from <3.6.0,>=3.2.0 to >=3.2.0,<7.3.0

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@v3.2.0...v7.2.6)

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

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

requirements.txt

@@ -2,6 +2,6 @@ default-values>=0.5.0
 dict2css>=0.2.3
 docutils==0.16
 domdf-python-tools>=2.9.0
-sphinx<3.6.0,>=3.2.0
+sphinx>=3.2.0,<7.3.0
 sphinx-panels>=0.5.1
 sphinx-toolbox>=2.13.0