vmtests post-test delete-artifact fails on fork

[mtardy]

See an example of workflow here:

Run geekyeggo/delete-artifact@65041433121f7239077fa20be14c0690f70569de
Error: HttpError: Resource not accessible by integration

It looks like a permissions error because this is running in the context of a fork, so we'll need to consider:

• Is it essential to delete the artifacts in case of success, Is saving 1GB of artifacts space necessary?
• If yes, is it okay to add the necessary permission for forks?