Fix markup. s/DestinationAmount/DeliveredAmount/

DestinationAmount is actually `DeliveredAmount` and (for better or worse) is set only when the full amount wasn't paid.

```c++
if (rc.result () == tesSUCCESS && rc.actualAmountOut != saDstAmount)
    mEngine->view ().setDeliveredAmount (rc.actualAmountOut);
```

References: 
[Payment Transactor](https://github.com/ripple/rippled/blob/2936bbfae86de2c94d5a1ee6ac129dd4f92de870/src/ripple/app/transactors/Payment.cpp#L292)
[Fields enumeration](https://github.com/ripple/rippled/blob/2936bbfae86de2c94d5a1ee6ac129dd4f92de870/src/ripple/data/protocol/SField.h#L358)