Remove cython from build requirements

Author: titusz

pyproject.toml

@@ -99,5 +99,5 @@ generate-setup-file = true
 script = "build.py"
 
 [build-system]
-requires = ["poetry-core>=1.0.0", "Cython>=3", "setuptools", "wheel"]
+requires = ["poetry-core", "setuptools", "wheel"]
 build-backend = "poetry.core.masonry.api"