Fixes#6014 by removing the double counting of the page scroll position.
The `getOffset()` utility function already includes the window's scroll position (see [here](20388c5766/packages/utils/src/dom/methods/getOffset.ts (L6-L7))). Double counting the scroll offset meant that the DataTable `onRowDragOver` event handler always through we were on the top-half of the row, preventing the indicator from being shown at the bottom of the row.