Update sphinx requirement from ~=7.2.5 to ~=7.2.6 (#345)

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@v7.2.5...v7.2.6)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs_requirements.txt

@@ -1,2 +1,2 @@
 furo~=2023.8.19
-sphinx~=7.2.5
+sphinx~=7.2.6