Update sphinx requirement from <5.2,>=4 to >=4,<7.3

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@v4.0.0...v7.2.6)

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

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

requirements.txt

@@ -26,7 +26,7 @@ pre-commit>=2.15,<2.21
 # Documentation
 # -----------------------
 myst-parser[linkify]>=0.15,<0.19
-sphinx>=4,<5.2
+sphinx>=4,<7.3
 sphinx-autobuild==2021.*
 sphinx-autodoc-typehints>=1.11,<1.20
 sphinx-copybutton<1