Pin sphinx to resolve docs build failures (#1347)

Author: krassowski

pyproject.toml

@@ -44,7 +44,9 @@ Tracker = "https://github.com/ipython/ipykernel/issues"
 
 [project.optional-dependencies]
 docs = [
-  "sphinx",
+  # Sphinx pinned until `sphinx-autodoc-typehints` issue is resolved:
+  # https://github.com/tox-dev/sphinx-autodoc-typehints/issues/523
+  "sphinx<8.2.0",
   "myst_parser",
   "pydata_sphinx_theme",
   "sphinxcontrib_github_alt",