Fix website generation workflow

.github/workflows/website.yml

@@ -31,7 +31,7 @@ jobs:
         run: scripts/update-website
       - name: Commit changes
         run: |
-          if git diff --quiet; then
+          if ! git diff --quiet; then
             git add --all
             git config user.name 'github-actions[bot]'
             git config user.email 'github-actions[bot]@users.noreply.github.com'