fix(ci): use --system flag for uv pip install

Added the `--system` flag to the `uv pip install` command in the GitHub Actions workflow.

This fixes the "No virtual environment found" error by instructing uv to install dependencies into the system's Python environment, which is appropriate for a CI context.

Author: google-labs-jules[bot]

.github/workflows/test_python.yml

@@ -45,7 +45,7 @@ jobs:
       - uses: astral-sh/setup-uv@v1
       - name: Install dev dependencies
         working-directory: ./Python
-        run: uv pip install -r requirements.txt
+        run: uv pip install --system -r requirements.txt
       - name: Lint
         working-directory: ./Python
         run: |