Call ruff in pdm environment

Author: mstimberg

.github/workflows/pytest-ubuntu.yaml

@@ -22,7 +22,7 @@ jobs:
 
     # Update output format to enable automatic inline annotations.
     - name: Run Ruff
-      run: ruff check --output-format=github .
+      run: pdm run ruff check --output-format=github .
 
     - name: Run tests
       run: |