actions/{setup-python,checkout} to v3

Author: janosh

.github/workflows/test.yml

@@ -22,10 +22,10 @@ jobs:
 
     steps:
       - name: Check out repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Set up python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v3
         with:
           python-version: 3.8
           cache: pip