build(deps): update sphinx requirement from <5.0,>=4.3 to >=4.3,<6.0

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/5.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.3.0...v5.0.0)

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

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

_building/building-requirements.txt

@@ -4,4 +4,4 @@ semantic_version>=2.9,<3.0
 jinja2>=3.0,<4.0
 PyYAML>=6.0,<7.0
 
-sphinx>=4.3,<5.0
+sphinx>=4.3,<6.0