docs(annotations): correct List for directives for Component

@component takes a List of directives https://github.com/angular/angular/blob/master/modules/angular2/src/core /annotations_impl/annotations.js#L867

Author: PatrickJS

modules/angular2/src/core/annotations_impl/annotations.js

@@ -832,7 +832,7 @@ export class Component extends Directive {
  * })
  * @View({
  * template: `{{greeter.greet('world')}}!`,
- * directives: Child
+ * directives: [Child]
  * })
  * class HelloWorld {
  * greeter:Greeter;