Wrong darkness behavior in BVE4 panel2.cfg cabs

Normally, images in BVE4 panels that don't have a "night" version provided are supposed to remain lit in low brightness areas and lots of panels have been made with that in mind. However, in Openbve daytime images without nighttime versions specified in panel2.cfg get shaded similarly to BVE2 panels, producing visual errors (look at the screen on the right for example)