Correct the "cumulative drawn amount" for loan: VNY8DM8+01.

The UI allowed the entry of incorrect Tranche Drawdowns. This has now been fixed
and it is not possible to repeat the error with the current UI.
Merge pull request #198 from alphagov/fix-cumulative-drawn-amount-for-vny8dm801

Correct the "cumulative drawn amount" for loan: VNY8DM8+01.