Fixed test broken by fixes to drag&drop #12406

Due to the fixes to the VDragAndDropManager the drop location became a
lot more accurate and so changed where the drops were made in the test.
To fix it I adjusted the pixel position within the drop target element to account for the
changed accuracy.

Change-Id: I60fec00a40c36fe0afcc7a4bacb2f7b101201b70