Update ISO urls in CI

[davidcassany]

I noted there are still missing some updates within the CI... In fact some ISO urls need to be addressed.

I can be checked by $ grep -rin iso_to_test .github. Note that URLS like:

https://download.opensuse.org/repositories/isv:/Rancher:/Elemental:/Staging:/Teal53/media/iso/elemental-teal.x86_64.iso

should be converted to

https://download.opensuse.org/repositories/isv:/Rancher:/Elemental:/Staging/containers/iso/elemental-teal.x86_64.iso

[kkaempf]

@ldevulder @juadk 👀

[ldevulder]

@kkaempf already on it.