chore(ci): adjust zone.js version for examples (#3015)

A partial followup to #3010

Author: chalin

public/docs/_examples/package.json

@@ -29,7 +29,7 @@
     "reflect-metadata": "^0.1.8",
     "rxjs": "5.0.0-rc.4",
     "systemjs": "0.19.39",
-    "zone.js": "0.7.2"
+    "zone.js": "^0.7.4"
   },
   "devDependencies": {
     "@types/angular": "^1.5.16",