consistently use actions/setup-python@v2 in CI workflows

Author: boegel

.github/workflows/linting.yml

@@ -7,7 +7,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: set up Python
-      uses: actions/setup-python@v1
+      uses: actions/setup-python@v2
       with:
         python-version: 3.8