Update sphinx requirement from <7.5,>=7.2.6 to >=7.2.6,<8.1

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@v7.2.6...v8.0.2)

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

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

Author: dependabot[bot]

pyproject.toml

@@ -45,7 +45,7 @@ dependencies = [
 
 [project.optional-dependencies]
 docs = [
-    "sphinx>=7.2.6,<7.5",
+    "sphinx>=7.2.6,<8.1",
     "sphinx-book-theme>=1.1.0,<1.2",
     "sphinxcontrib-bibtex>=2.6.2,<2.7",
     "myst-parser>=2.0.0,<3.1",