subtrees replaced with submodules

Author: James-E-A

.github/workflows/python_build.yaml

@@ -8,6 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - run: git clone --recurse-submodules --shallow-submodules
       - uses: actions/setup-python@v4
       - name: install dev requirements
         run: python -m pip install "cibuildwheel"