Update sphinx-autodoc-typehints requirement from <=1.23.0 to <=2.1.0

Updates the requirements on [sphinx-autodoc-typehints](https://github.com/tox-dev/sphinx-autodoc-typehints) to permit the latest version.
- [Release notes](https://github.com/tox-dev/sphinx-autodoc-typehints/releases)
- [Changelog](https://github.com/tox-dev/sphinx-autodoc-typehints/blob/main/CHANGELOG.md)
- [Commits](tox-dev/sphinx-autodoc-typehints@1.0.0...2.1.0)

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

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

pyproject.toml

@@ -61,7 +61,7 @@ dev = [
   "myst-parser==1.0.0",
   "sphinx-copybutton==0.5.2",
   "sphinx-autobuild==2021.3.14",
-  "sphinx-autodoc-typehints<=1.23.0",
+  "sphinx-autodoc-typehints<=2.1.0",
   "packaging"
 ]
 examples = [