Checkout discount code input styling on mobile

[arraypress]

Expected Behavior

It looks like the checkout discount code is not properly styled on the demo site/theme. I would expect this to look the same (with the border) as the totals below to keep it cohesive design wise.

Actual Behavior

See screenshot for reference:

[spencerfinnell]

The original intended design is correct on the desktop: https://cloudup.com/crGCjKSycNb -- mobile just needs some spacing updates.

To match the "Totals" box you can add the .card class to the coupon form wrapper.

https://github.com/woocommerce/woocommerce/blob/master/templates/checkout/form-coupon.php#L29