build(deps): update sphinx requirement from ~=4.1 to ~=4.3

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/4.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.1.0...v4.3.0)

---
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~=2.8
 jinja2~=2.11
 PyYAML~=5.4
 
-sphinx~=4.1
+sphinx~=4.3