title: Woocommerce - Call to undefined method WC_Order::get_order_discount()
body: <p>I just updated to Woocommerce 3.3.5 and it appears that the <code>get_order_discount()</code> function has been deprecated. The plugin that is calling it is <strong>woocommerce-gateway-paypal-pro</strong> which has not put out any updates to resolve this issue. I searched through Woocommerce's function reference and for the life of me cannot find the function that replaces <code>get_order_discount()</code>. </p>
  
  <p>If anyone with a bit of <strong>Woocommerce</strong> expertise could point me in the right direction it would be greatly appreciated.</p>