docs: missing images on two pages

[neigeantre]

On this page an image cannot be loaded, because the link to it is broken : https://osrd.fr/images/docs/railway-wiki/signalling/image-073.jpg

Indeed the image image-073.jpg cannot be found in the image folder

Same goes for image-074.jpg in https://osrd.fr/fr/docs/railway-wiki/signalling/operation-modes/double-track-lines/temporary-single-track-of-permanent-nature/

[woshilapin]

Seems like this image was never here from the beginning. The article got introduced in b1cf075 which doesn’t contain the image it refers too. I guess it’s lost and I don’t see a way we could salvage that. Maybe we should just remove those links (and possibly adapt the text around if it depends on the image).