enh(ui): add updated image for VTK sphere loading test
Description
This updates the screenshot of the VTK sphere loading test for sight!916 (merged). The volume renderer is no longer starts before an image is loaded, and then the sphere is now the only object in the scene, thus the camera is centered on it.
How to test it?
You sight!916 (merged) and run sightviewerguitest sight::sightviewer::test::ui::LoadVtk::test