Update sphinx requirement from <8,>=5 to >=5,<9

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/v8.0.2/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v5.0.0...v8.0.2)

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

Signed-off-by: dependabot[bot] <[email protected]>

pyproject.toml

@@ -50,7 +50,7 @@ dev = ["pre-commit>=2.12.1"]
 tests = ["flake8", "pytest", "pytest-mock", "pytest-split", "pytest-cov", "types-setuptools"]
 docs = [
     "sphinx-copybutton==0.5.2",
-    "sphinx>=5,<8",
+    "sphinx>=5,<9",
     "sphinx_design==0.6.1",
     "myst-nb==1.1.1",
     "sphinx-book-theme==1.1.3",