fix: pin Cython to <3.1 (#228)

Author: bdraco

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ['setuptools>=77.0', 'Cython>=3', "poetry-core>=2.0.0"]
+requires = ['setuptools>=77.0', 'Cython>=3,<3.1', "poetry-core>=2.0.0"]
 build-backend = "poetry.core.masonry.api"
 
 [project]