Simplify arrow function syntax for handlers (#309)

Author: NullVoxPopuli

content/4-component-composition/2-emit-to-parent/emberPolaris/app.gjs

@@ -5,12 +5,12 @@ import AnswerButton from "./answer-button";
 export default class App extends Component {
   @tracked isHappy = true;
 
-  handleYes = () => (this.isHappy = true);
-  handleNo = () => (this.isHappy = false);
+  handleYes = () => this.isHappy = true;
+  handleNo = () => this.isHappy = false;
 
   <template>
     <p>Are you happy?</p>
     <AnswerButton @onYes={{this.handleYes}} @onNo={{this.handleNo}} />
     <p style="font-size: 50px;">{{if this.isHappy "😀" "😥"}}</p>
   </template>
-}
+}