fixup! fixup! test(cdk-experimental/listbox): add unit tests

Author: wagnermaciel

src/cdk-experimental/listbox/listbox.spec.ts

@@ -761,7 +761,6 @@ interface TestOption {
       }
     </ul>
   `,
-  standalone: true,
   imports: [CdkListbox, CdkOption],
 })
 class ListboxExample {
@@ -793,7 +792,6 @@ class ListboxExample {
       <li cdkOption [value]="2">2</li>
     </ul>
   `,
-  standalone: true,
   imports: [CdkListbox, CdkOption],
 })
 class DefaultListboxExample {}