Eliminar la clase activa de todo Li JavaScript

<!-- w3.js brings the simple and fast solution -->
<script src="https://www.w3schools.com/lib/w3.js"></script>
<ul>
  <li class="ready">
</li>
  <li class="ready">
</li>
  <li class="ready">
</li>
</ul>
<button onclick="w3.removeClass('li','ready');"></button>
Helpless Horse