fix scheduled unit tests action, use python 3.11

Author: timvink

.github/workflows/scheduled_unittests.yml

@@ -20,7 +20,7 @@ jobs:
     - name: Setup Python
       uses: actions/setup-python@master
       with:
-        python-version: 3.10
+        python-version: "3.11"
 
     - name: Install dependencies
       run: |