Update sphinx requirement from <6,>=4.4.0 to >=4.4.0,<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)
- [Commits](sphinx-doc/sphinx@v4.4.0...v6.0.0)

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

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

pyproject.toml

@@ -110,7 +110,7 @@ demo = [
   "ipython",
 ]
 doc = [
-  "sphinx>=4.4.0,<6",
+  "sphinx>=4.4.0,<7",
   "myst-parser==0.18.1",
   "Jinja2==3.1.2",
   "alabaster",