fixing workflow

.gitea/workflows/tests.yaml

@@ -4,15 +4,12 @@ on: [push, workflow_dispatch]
 
 jobs:
   unittests:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - name: Check out repository code
         uses: actions/checkout@v4
       - name: Set up Python
         uses: actions/setup-python@v5
-        with:
-          python-version: '3.13'
-          cache: 'pip'
       - name: Test with unittest
         run: |
           pip install unittest