fix typo: close providers array in zone.js snippet

Author: JohannesHoppe

blog/2025-11-angular21/README.md

@@ -59,6 +59,7 @@ export const appConfig: ApplicationConfig = {
     // ...
     // VERALTETE Change Detection mit Zone.js aktivieren
     provideZoneChangeDetection({ eventCoalescing: true }),
+  ]
 };
 ```