Disallow unused properties JS-0715

Unused properties should be eliminated.

Bad Practice

<!-- (`count` property not used) -->
<template>
  <div>{{ cnt }}</div>
</template>
<script>
  export default {
    props: ['count']
  }
</script>

Recommended

<template>
  <div>{{ count }}</div>
</template>
<script>
  export default {
    props: ['count']
  }
</script>