use v3 for checkout and v4 for python (#39)

Author: splch

.github/workflows/test_notebooks.yml

@@ -7,10 +7,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Check out code
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
 
     - name: Set up Python
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v4
       with:
         python-version: '3.x'