message: fix first operator
diff: @@ -33,7 +33,7 @@ will emit `1`, `4`, `9`. Another useful operator is [`first`](/api/operators/fi
  import { of } from 'rxjs';
  import { first } from 'rxjs/operators';
  -first()(of(1, 2, 3).subscribe((v) => console.log(`value: ${v}`));
  +first()(of(1, 2, 3)).subscribe((v) => console.log(`value: ${v}`));
  // Logs:
  // value: 1
  