fix transforming sortable items

[yonathan06]

I experienced an issue where sortable items with different heights were not transformed properly The issue was that the delta was calculated as target.x - current.x (or target.y - current.y) the delta was the diff between an item and the one before/after them, instead of the size of the dragged item Changed it to transform based on the size of the dragged item

here is a reproduction repo https://stackblitz.com/edit/solidjs-templates-atuhev

[MGaetan89]

It looks like this change has landed in master in https://github.com/robolectric/robolectric/commit/b45b15d8db80c63609bfdce386cd786efd6618cf. So I'm closing this PR.