Deprecation error with simple keyboard shortcut implementation

I implemtented two simple keyboard shortcuts in my app:

```
{{on-key 'ctrl+m' this.toggleVisibility}}
{{on-key 'ctrl+b' this.toggleVisibility}}
```

These toggle the visibility of something:

```
import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { action } from '@ember/object';

export default class styleguideComponent extends Component {
@tracked visibility = true;
@service router;

@action
toggleVisibility() {
this.visibility = !this.visibility
}
}

```

However, I get a long depreciation [stack trace](https://gist.github.com/Wolfr/cdaa8acc78ab9ff5a1c908b1e6c761a6) . I think I used the latest syntax as documented [here](http://adopted-ember-addons.github.io/ember-keyboard/usage).

If I remove the 2nd shortcut, I don't get the stack trace. However, it is recommended in the docs to do it this way for multiple shortcuts.

Would anyone have an idea why I am getting this stack trace? I loved the simplicity of this package btw.

Start by reproducing the two `on-key` shortcuts from the issue and compare them with the multiple-shortcut usage documented at the linked Ember Keyboard guide. Inspect the linked deprecation stack trace to identify the failing path. Done means both shortcuts toggle visibility without producing the deprecation trace.

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