chore(deps): update dependency socket.io to v2

Author: mend-for-github-com[bot]

assets/wmt/reveal/package.json

@@ -38,7 +38,7 @@
     "grunt-zip": "~0.17.1",
     "mustache": "~2.2.1",
     "node-sass": "~3.13.0",
-    "socket.io": "^1.4.8"
+    "socket.io": "^2.5.0"
   },
   "license": "MIT"
 }