websites: Move the job for images.apertis.org under websites/

The job was named packages/build-apertis-website even if it had nothing to do with packages, and the template lived under image-recipes/ even if it's not an image-building recipe (at the moment it checks out the same repository though).

Create a new websites/ folder and move the job there as websites/images-apertis-org (both for the template and the actual job).