Simplify CI workflow to use python container directly

.gitea/workflows/ci.yml

@@ -9,14 +9,7 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    container: python:3.11-slim
     steps:
-      - name: Set up Python
-        run: |
-          apt-get update
-          apt-get install -y python3 python3-pip python3-venv
-          python3 --version
-          pip3 --version
       - name: Install package
-        run: pip3 install -e . pytest pytest-asyncio
-      - name: Run tests
-        run: python3 -m pytest tests/ -v
+        run: pip install -e . pytest pytest-asyncio && python -m pytest tests/ -v