docs: fix the code sample displayed in the "reusable animations" guide (#37262)

Currently the code sample displayed in this guide is not a valid.
The `trigger` is directly used in the `@Component` decorator.
It should instead be in the `animations` array of the `@Component` decorator.

PR Close #37262

aio/content/examples/animations/src/app/open-close.component.3.ts

@@ -1,29 +1,12 @@
 // #docplaster
 // #docregion reusable
 import { Component } from '@angular/core';
-import { useAnimation, transition, trigger, style, animate } from '@angular/animations';
+import { transition, trigger, useAnimation } from '@angular/animations';
 import { transAnimation } from './animations';
 
 @Component({
-// #enddocregion reusable
   selector: 'app-open-close-reusable',
-// #docregion runtime
   animations: [
-    transition('open => closed', [
-      style({
-        height: '200 px',
-        opacity: '{{ opacity }}',
-        backgroundcolor: 'yelow'
-      }),
-      animate('{{ time }}'),
-    ], {
-        params: {
-          time: '1s',
-          opacity: '1'
-        }
-      }),
-// #enddocregion runtime
-// #docregion reusable
     trigger('openClose', [
       transition('open => closed', [
         useAnimation(transAnimation, {
@@ -36,10 +19,9 @@ import { transAnimation } from './animations';
         })
       ])
     ])
-// #enddocregion reusable
+  ],
   templateUrl: 'open-close.component.html',
   styleUrls: ['open-close.component.css']
-// #docregion reusable
 })
 // #enddocregion reusable
 export class OpenCloseReusableComponent { }