bug#40882: website: screenshots should show configuration.scm

[Jonathan Brielmaier]

A German youtuber did a review of Guix System[0]. He couldn't find the
configuration.scm file of his system, because he looked at
https://guix.gnu.org/screenshots/virtual-machine/. On the screenshot
it's named os-config.scm, so he searched via find. But couldn't find it.

I think we should recreate this screenshot and show the file as
configuration.scm or even as /run/current-system/configuration.scm :)

What do you think?

[0] https://www.youtube.com/watch?v=IKsXecNJ_nE