docs(dart): update angular.io/dart's link to change log

Author: kwalrath

public/docs/dart/latest/_data.json

@@ -3,7 +3,7 @@
     "icon": "home",
     "title": "Angular Docs",
     "menuTitle": "Docs Home",
-    "banner": "Welcome to <b>angular.io/dart</b>! The current Angular 2 Dart release is <b>beta.18</b>. Consult the <a href='https://github.com/angular/angular/blob/master/CHANGELOG.md' target='_blank'>Change Log</a> about recent enhancements, fixes, and breaking changes."
+    "banner": "Welcome to <b>angular.io/dart</b>! The current Angular 2 Dart release is <b>beta.18</b>. Consult the <a href='https://github.com/dart-lang/angular2/blob/master/CHANGELOG.md' target='_blank'>Change Log</a> about recent enhancements, fixes, and breaking changes."
   },
 
   "quickstart": {