[ci] forego uv in favour of plain python venv

.woodpecker/workflow.yaml

@@ -22,7 +22,9 @@ steps:
       - markdownlint-cli2 .
 
   - name: Run Tests
-    image: ghcr.io/astral-uv/uv:python${PYTHON_VERSION}-trixie-slim
+    image: python:${PYTHON_VERSION}-slim
     commands:
-      - uv install
-      - uv run pytest tests.py
+      - python -m venv venv
+      - . venv/bin/activate
+      - python -m pip install --disable-pip-version-check --no-input --quiet -r requirements.txt -r requirements.dev.txt
+      - python -m pytest tests.py