docs: remove unused css file from counter component (ngrx#3002)

Closes ngrx#2989

Author: AlmaniaM

projects/ngrx.io/content/examples/store/src/app/my-counter/my-counter.component.css

@@ -6,7 +6,6 @@ import { increment, decrement, reset } from '../counter.actions';
 @Component({
   selector: 'app-my-counter',
   templateUrl: './my-counter.component.html',
-  styleUrls: ['./my-counter.component.css'],
 })
 export class MyCounterComponent {
   count$: Observable<number>;