Update actions/setup-node action to v6

Author: renovate[bot]

.github/workflows/update.yml

@@ -13,7 +13,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Update Sitemap
-        uses: actions/setup-node@v3
+        uses: actions/setup-node@v6
         with:
           node-version: 18.x
           cache: "npm"