ci: bump actions/setup-node to v6 for Node 24 runtime (#8212)

Author: soyuka

.github/workflows/ci.yml

@@ -224,7 +224,7 @@ jobs:
           composer global config allow-plugins.soyuka/pmu true --no-interaction
           composer global link .
       - name: Setup Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
           node-version: '20'
       - name: Install Redocly CLI