Fixed the used value of the giftcard at checkout

The value shown on the checkout page of the amount of the gift card used was:
     'value'	=> woocommerce_price( -1 * $giftCardPayment[0] )

There was no need use a array index since the value retrieved as the amount was not in an index, it was changed to:
     'value'	=> woocommerce_price( -1 * $giftCardPayment )