Update sphinx requirement from ~=6.1.3 to ~=7.2.6

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@v6.1.3...v7.2.6)

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

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

pyproject.toml

@@ -90,7 +90,7 @@ ci = [
 ]
 docs = [
     'myst-parser~=1.0.0',
-    'sphinx~=6.1.3',
+    'sphinx~=7.2.6',
     'sphinx-click~=4.4.0',
     'sphinx-markdown-builder~=0.5.5',
     'mike~=1.1.2',