Update ruff yml

Author: simonengstler

.github/workflows/ruff_check.yml

@@ -7,4 +7,6 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: astral-sh/ruff-action@v3
-
+      - run: ruff format --check --diff
+        with:
+          src: "./backend"