Only use width/height in animateEndDragToDesktop.

Removes the use of startAbsBounds position in animateEndDragToDesktop in
favor of using width/height instead. This fixes an animation issue where
right/bottom split tasks would have an additional, unintended offset due
to task position not being (0, 0).

Bug: 323378048
Test: Manual
Flag: EXEMPT, minor change
Change-Id: If212628d13e746b069c27f16b2ed5194f4d57111