message: Fix hidden attribute
diff: -{{#if enabled}}
  {{#bs-modal class=modalClass open=open onSubmit=(action "submit") onHidden=(action 'hideDialog') as |modal|}}
  {{#modal.body}}
  {{#if active}}
  {{/modal.footer}}
  {{/bs-modal}}
  -
  - <button class="FeedbackButton {{if open 'FeedbackButton--open'}}" onclick={{action 'showDialog'}} aria-label={{t 'feedback.title'}}>
  +<button class="FeedbackButton {{if open 'FeedbackButton--open'}}" onclick={{action 'showDialog'}} aria-label={{t 'feedback.title'}} hidden={{not enabled}}>
  {{t 'feedback.button_text'}}
  </button>
  -{{/if}}
  