fix: Change the way checking if the file changed

Signed-off-by: Awiteb <a@4rs.nl>

.forgejo/workflows/contributors.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Update Contributors
         run: |
           ./bin/just contributors
-          if [ -n "$(git status --porcelain)" ]; then
+          if git diff --name-only | grep -q "^CONTRIBUTORS.md$"; then
             git config user.name forgejo-actions
             git config user.email forgejo-actions@noreply.localhost
             git add CONTRIBUTORS.md