Use actions/checkout@v3

Author: wch

.github/workflows/pytest.yaml

@@ -17,7 +17,7 @@ jobs:
       fail-fast: false
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v2
         with:
@@ -46,7 +46,7 @@ jobs:
     if: github.event_name == 'release'
     needs: [build]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: "Set up Python 3.8"
         uses: actions/setup-python@v2
         with: