Update Node.js to ~22.21.0

Author: renovate[bot]

themes/hugo-theme-altinn/static/revealjs/plugin/multiplex/package.json

@@ -7,7 +7,7 @@
     "start": "node index.js"
   },
   "engines": {
-    "node": "~22.19.0"
+    "node": "~22.21.0"
   },
   "dependencies": {
     "express": "~5.1.0",