[test] Allow CLI integration test to be retryable (#85586)
Fixes https://github.com/vercel/next.js/actions/runs/18937795131/job/54068900147#step:34:1879
`--experimental-https` test creates a cert relying on no cert existing in the default path. When it passes, it doesn't cleanup. Retrying that test file due to an unrelated failure would therefore always fail. Now we ensure no cert exists.
