Experimental: Announcement status invalid

When dragging an item in the experimental [multiple sortable lists](https://next.dndkit.com/react/guides/multiple-sortable-lists) example, the value of the `id="dnd-kit-announcement-2"` gets set to invalid values, for example:

> Draggable item **A0** was moved over droppable target **A0**.

When the item is dropped, the value changes to:

> Draggable item **A0** was dropped over droppable target **A0**

I'm assuming this is a bug as an element cannot be dropped over itself


Start with the experimental multiple sortable lists example linked in the issue and inspect the element with id dnd-kit-announcement-2 during drag and drop. Reproduce the behavior with item A0 and determine why the announcements identify the dragged item as its own target; done means the announcement no longer reports an invalid self-target.

Written by the indexing model from the issue text.