Don't pre-clone submodules on CI, at least for now

This has actions/checkout no longer automatically clone submodules
in the CI test workflows. This change is for the purpose of
reproducing gitpython-developers#1713, to allow the forthcoming fix for it to be
tested.

However, continuing to rely on init-tests-after-clone.sh to get the
submodules would serve as a kind of regression testing for gitpython-developers#1713.
So it is unclear at this time if and when this change should be
undone.

.github/workflows/cygwin-test.yml

@@ -26,7 +26,6 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-        submodules: recursive
 
     - name: Install Cygwin
       uses: cygwin/cygwin-install-action@v4

.github/workflows/pythonpackage.yml

@@ -27,7 +27,6 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-        submodules: recursive
 
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v4