pinned sphinx

Author: alitinet

pyproject.toml

@@ -45,7 +45,7 @@ optional-dependencies.doc = [
   "pandas",
   # Until pybtex >0.24.0 releases: https://bitbucket.org/pybtex-devs/pybtex/issues/169/
   "setuptools",
-  "sphinx>=8.1",
+  "sphinx<9", #>=8.1
   "sphinx-autodoc-typehints",
   "sphinx-book-theme>=1",
   "sphinx-copybutton",