Investigate flakey cross-origin stylesheet test

I've seen this test fail a few times, need to investigate https://app.circleci.com/pipelines/github/dequelabs/axe-core/5782/workflows/168c78f9-f61d-4184-80d9-64c4b4335df4/jobs/63762

```
Chrome 120.0.0.0 (Linux x86_64): Executed 1427 of 1453 (1 FAILED) (skipped 26) (16.76 secs / 13.154 secs)
Firefox 121.0 (Linux x86_64): Executed 1427 of 1453 (skipped 26) SUCCESS (19.534 secs / 14.565 secs)
TOTAL: 1 FAILED, 2853 SUCCESS

1) returns cross-origin stylesheet
axe.utils.parseCrossOriginStylesheet
Error: done() invoked with non-Error: [object ProgressEvent]
at test/core/utils/parse-crossorigin-stylesheet.js:58:9
```