Wrong Pub dev documentation

There is an error in the pub.dev documentation that can hinder beginners.

Here you can see that the documentation suggests this code,

But when putting this in the code it is possible to see that it does not work due to the lack of 'await' in the documentation

The correct thing would be
```dart
final catsBox = await collection.openBox('cats');
```

Start with the pub.dev documentation example shown in the issue and compare it with the reported Dart error. Update the openBox example to include await, then verify that the corrected snippet is valid Dart and matches the documented asynchronous API.

Written by the indexing model from the issue text.