Use Python 3.9 for pyppeeteer

.github/workflows/integration-tests.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: '3.x'
+          python-version: '3.9'
           architecture: x64
       - name: Install dependencies
         run: |