No longer use system python

Author: mslw

.github/workflows/run-server-tests.yml

@@ -15,11 +15,10 @@ jobs:
       - name: Set up Python 3.11
         run: uv python install
       - name: Install dependencies
-        env:
-          UV_SYSTEM_PYTHON: 1
         run: |
           uv tool install git-annex
           uv tool install datalad
+          uv venv
           uv pip install -r requirements-devel.txt
           echo which git-annex
           which git-annex