Use python 3.7 for examples test

ScalaPy requires python 3.7 at minimum

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: 3.6
+        python-version: 3.7
     - name: Install python dependencies
       run: |
         python -m pip install --upgrade pip