Capture does not work through API

[rain2o]

When using Magento's API endpoint /V1/order/{orderId}/invoice on an order with Heartland as the payment method the <preference for="Magento\Sales\Model\Order\Payment".../> is not active because it is set in the adminhtml scope. Because this preference is not active the capture action does not happen as the canCapture function always returns false.

Suggested fix is to move the <preference> to the global di.xml file. I will submit a corresponding PR.