Revert "refactor: use new Http library in playground (#29355)"

This reverts commit acfcf90528.

modules/playground/src/jsonp/app/jsonp_comp.ts

@@ -6,12 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {HttpClient} from '@angular/common/http';
 import {Component} from '@angular/core';
-
-interface Person {
-  name: string;
-}
+import {Jsonp} from '@angular/http';
 
 @Component({
   selector: 'jsonp-app',
@@ -19,14 +15,14 @@ interface Person {
     <h1>people</h1>
     <ul class="people">
       <li *ngFor="let person of people">
-        hello, {{person.name}}
+        hello, {{person['name']}}
       </li>
     </ul>
   `
 })
 export class JsonpCmp {
-  people: Person[];
-  constructor(http: HttpClient) {
-    http.jsonp('./people.json', 'callback').subscribe(res => this.people = res);
+  people: Object;
+  constructor(jsonp: Jsonp) {
+    jsonp.get('./people.json?callback=JSONP_CALLBACK').subscribe(res => this.people = res.json());
   }
 }