Actually test dev env in CI

Author: hynek

.github/workflows/ci.yml

@@ -204,7 +204,7 @@ jobs:
       - uses: hynek/setup-cached-uv@757bedc3f972eb7227a1aa657651f15a8527c817 # v2.3.0
 
       - run: uv venv --python $(cat .python-version-default)
-      - run: uv pip install -e .[dev]
+      - run: uv pip install -e . --group dev
 
       - name: Ensure we can import attr and attrs packages
         run: |