Remove the elevation on the DragView to avoid shadows underneath

In b/297952359 we are seeing that widgets with clipped outline
 elements end up showing shadows below their drag view. Which
 due to not maintaining clipping looks further bad.

It seems like, we don't really need the elevation for drag
view anymore - and presumably it was added for older android
 versions for shadow for folders. But, they don't have them
  anymore, so, removing elevation now.

 Note: The issue that during drag and drop, the dragged preview
 not showing clip to outline or shadows within widget's views is
 a separate issue related to the Picture API usage during drag
  and drop.

Bug: 297952359
Test: Screen record in comments
Flag: EXEMPT Bugfix

Change-Id: If31a0275938afe374d269a46cc950970033323f9