GitHub seems to think it is copyrightable, personally I doubt it is, simply because a human didn't create it and the process it was created by was automatic with no creativity.
Also, there's no way for anyone to know what portion of code that I commit was hand written vs. generated, so you kind of have to treat it all as written by the committer anyway.
Though this does bring up interesting questions about what happens with things like automated PRs that fix bugs / update dependencies... are those then non-copyrightable? ¯\_(ツ)_/¯
Just as much as a hero riding off into the sunset is not copyrightable in a movie script. However, a hero riding off into the sunset with bananas in the pistol holsters would be.
This is what I would want to hear more about when discussing if Copilot violates copyright.