Simplify git diff command in workflow

Author: CFenner

.github/workflows/format.yml

@@ -42,5 +42,5 @@ jobs:
       - name: Update deprecation database
         run: python check_deprecations.py --update
       - name: Verify no changes
-        run: git diff --name-only --exit-code
+        run: git diff --exit-code
         if: always()