docs(dialog): change afterOpen to afterOpened in example (#17087)

Author: peterblazejewicz

src/dev-app/dialog/dialog-demo.ts

@@ -53,7 +53,7 @@ export class DialogDemo {
     // Possible useful example for the open and closeAll events.
     // Adding a class to the body if a dialog opens and
     // removing it after all open dialogs are closed
-    dialog.afterOpen.subscribe(() => {
+    dialog.afterOpened.subscribe(() => {
       if (!doc.body.classList.contains('no-scroll')) {
         doc.body.classList.add('no-scroll');
       }