docs(core): replace angular2/angular2 with the right barrel import.

Related to #5710
Closes #5847

modules/angular2/src/http/static_request.ts

@@ -25,7 +25,7 @@ import {
  * where it may be useful to generate a `Request` with arbitrary headers and search params.
  *
  * ```typescript
- * import {Injectable, Injector} from 'angular2/angular2';
+ * import {Injectable, Injector} from 'angular2/core';
  * import {HTTP_PROVIDERS, Http, Request, RequestMethod} from 'angular2/http';
  *
  * @Injectable()