Replace inaccurate image of empty state usage in data table on website

### Summary

Change the image of the empty state component being used in a data table. Its appearance does not match the solution we provide for displaying an empty state component.

### 💬 Description

See the first image on the [empty state guidance page](https://design.sis.gov.uk/components/feedback-progress/empty-state/):

It shows an empty state component being used in a data table, but the problem is that we do not provide a solution which looks like this. We provide a [slotted empty state option](https://design.sis.gov.uk/components/data-display/data-table/code/#slotted-empty-state), but it simply appears in place of the rows of data, and doesn't look like the overlay in that image.

The image is misleading and has caused confusion for a customer as they were wondering how to get their empty state to look like the image.

This image needs updating by a designer to match the appearance of the slotted empty state, i.e. no overlay or central alignment.

### 💰 Use value

This will prevent customers from being confused about how to implement what is shown in the image