Update dependency socket.io to v2 [SECURITY] (#546)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

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

@@ -13,7 +13,7 @@
     "express": "~4.19.0",
     "grunt-cli": "~1.4.0",
     "mustache": "~4.2.0",
-    "socket.io": "~1.7.0"
+    "socket.io": "~2.5.1"
   },
   "license": "MIT"
 }