Run linting test on 3.9

Author: oschwald

.github/workflows/lint.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
 
       - name: Install dependencies
         run: |