ci: fix artifact build #4137
Description
It looks like what I did in #4126 was a bit too aggressive -- the artifact build isn't running on pull requests any more (hurray!) but now it's not running on anything. I think we'd like it to run on main and only main, and only run on the main intel/cve-bin-tool repo so I don't get messages about people's forks.
It's likely a typo or some other reasonably trivial fix, but it may be hard to find because debugging yml that runs only on main is the worst. If you intend to work on this, you'll probably want to take the repo name check out so you can test it on your fork, then put it back in just before making a PR.