Update sphinx requirement from <5.4,>=3.0 to >=3.0,<6.3 (#814)

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@v3.0.0...v6.2.0)

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

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

Author: dependabot[bot]

docs/sphinx-requirements.txt

@@ -1,5 +1,5 @@
 # Sphinx builds the documentation
-sphinx>=3.0,<5.4
+sphinx>=3.0,<6.3
 
 # Sphinx dependencies
 Pygments>=2.6.1