fix deprecation bug in setup-python@v3 by upgrading to v5, reported here: actions/setup-python#1085

Author: annalena-k

.github/workflows/pytest.yml

@@ -18,7 +18,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Set up Python 3.10
-        uses: actions/setup-python@v3
+        uses: actions/setup-python@v5
         with:
           python-version: '3.10'
           cache: 'pip'