[FIX] examples: update benchmarks code to new structure

examples/benchmarks/app.js

@@ -25,7 +25,7 @@ const template = `
         </div>
     </div>`;
 
-export class App extends owl.core.Component {
+export class App extends owl.Component {
   constructor(parent, props) {
     super(parent, props);
     this.inlineTemplate = template;

examples/benchmarks/counter.js

@@ -1,4 +1,4 @@
-export class Counter extends owl.core.Component {
+export class Counter extends owl.Component {
   inlineTemplate = `
     <div>
       <button t-on-click="increment(-1)">-</button>

examples/benchmarks/main.js

@@ -2,7 +2,7 @@ import { App } from "./app.js";
 
 function createApp(el) {
   const env = {
-    qweb: new owl.core.QWeb()
+    qweb: new owl.QWeb()
   };
   const app = new App(env, { initialState: 13 });
   app.mount(el);

examples/benchmarks/message.js

@@ -1,6 +1,6 @@
 import { Counter } from "./counter.js";
 
-export class Message extends owl.core.Component {
+export class Message extends owl.Component {
   inlineTemplate = `
     <div class="message">
         <span class="author"><t t-esc="props.author"/></span>