Remove drag pick-up logic in NestedDraggable

This CL removes the drag pick-up logic in NestedDraggable as it's
currently broken. See b/386916947#comment1 for details.

Bug: 386916947
Test: Removed feature that was not working or even test properly
Flag: EXEMPT NestedDraggable is not used anywhere yet
Change-Id: Ie659f41ec5cf99314aee69c0d8f99f96e6fa3305