Description:
Images of the Image block don't use their largest size when expanded by the lightbox, but the one selected by the editor.

Acceptance criteria:
Images of the Image block use their largest size when expanded by the lightbox.

Steps to replicate this bug:

1. Add a new Image block with an image.
2. Change the size of the image (for instance, to "thumbnail" or "medium").
3. Save the changes, go to the front, and click on the image.
4. When the lightbox opens, the image won't go large, but keep the same size selected in step 2.

External links:

• https://github.com/greenpeace/planet4-master-theme/pull/2430#issuecomment-2449536685