Use actions/setup-python@v4

Author: wch

.github/workflows/pytest.yaml

@@ -48,7 +48,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: "Set up Python 3.8"
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.8"
       - name: Install dependencies