Remove redundant a11y announcement upon removal of workspace item.

When a workspace item is removed, launcher currently shows a Snackbar which contains a message saying "item removed". This renders the a11y announcement in DeleteDropTarget#onAccessibilityDrop redundant since it's saying exactly the same string.


Bug: 378032433
Change-Id: I6eda4bb449f1d1fd4441a68b3129b0ab2d2c19a3
Test: manual
Flag: EXEMPT bugfix