Fix dead link to source of Binding.scala TodoMVC application (#1669)

Fixes #1669 

learn.json

-{
+{
 	"angularjs": {
 		"name": "AngularJS",
 		"description": "HTML is great for declaring static documents, but it falters when we try to use it for declaring dynamic views in web-applications. AngularJS lets you extend HTML vocabulary for your application. The resulting environment is extraordinarily expressive, readable, and quick to develop.",
@@ -1919,8 +1919,7 @@
 		"examples": [{
 			"type": "backend",
 			"name": "This TodoMVC application",
-			"url": "examples/binding-scala",
-			"source_url": "https://github.com/ThoughtWorksInc/todo"
+			"url": "examples/binding-scala"
 		}, {
 			"type": "backend",
 			"name": "Other live DEMOs",