ci: tighten security of checkout action

Author: foosel

.github/workflows/publish-to-github-pages.yml

@@ -19,7 +19,9 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
+        with:
+          persist-credentials: false
 
       - name: Set up Node.js
         uses: actions/setup-node@v6