Reduce Cython version to install scikit-learn min version

Author: lajohn4747

.github/workflows/minimum.yml

@@ -21,6 +21,7 @@ jobs:
     - name: Install dependencies
       run: |
           python -m pip install --upgrade pip
+          python -m pip install Cython==0.29.24
           python -m pip install invoke .[test]
     - name: Test with minimum versions
       run: invoke minimum