⬆️ Update sphinx requirement from <7.4.0,>=5 to >=5,<8.2.0 (#689)

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@v5.0.0...v8.1.0)

---
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>

requirements-doc.txt

@@ -10,7 +10,7 @@ taichi==1.7.0
 # document requirements
 pandoc
 Jinja2
-sphinx>=5, <7.4.0
+sphinx>=5, <8.2.0
 myst-nb
 sphinx_thebe
 sphinx-autodoc-typehints