Install setuptools when building release

Apparently, this is no longer installed by default.

.github/workflows/release.yml

@@ -20,6 +20,8 @@ jobs:
         uses: actions/setup-python@v4
         with:
           python-version: 3.x
+      - name: Install build dependencies   # needed by our setup.py
+        run: python -m pip install setuptools
       - name: Build the Python distribution
         run: python setup.py sdist
       - name: Publish distribution to PyPI