Deprecation warning in Ember 3.4

### Version of x-select: 3.1.1

### Ember Version / Ember CLI Version:

**Ember Version:** 3.4
**Ember CLI Version:** 3.4.3
### Expected Behavior

no deprecation warnings

### Actual Behavior

After upgrade to Ember 3.4 I am getting deprecation warnings

DEPRECATION: You called .sendAction("action") but Component#sendAction is deprecated. Please use closure actions instead. [deprecation id: ember-component.send-action] See https://emberjs.com/deprecations/v3.x#toc_ember-component-send-action for more details.

### Steps To Reproduce:
I have deprecation warning for each component use. I use exactly the same method of invocation like described in ReadMe

```
{{#x-select value=selections multiple=true action="selectionsChanged" as |xs|}}

etc
```

Start with the README invocation shown in the issue and reproduce the warning using Ember 3.4.3 and x-select 3.1.1. Trace the x-select action handling associated with the `action="selectionsChanged"` usage; done means the same component usage no longer emits the Component#sendAction deprecation warning.

Rédigé par le modèle d'indexation à partir du texte de l'issue.