Intermittent PASS in `/css/css-animations/animation-iteration-event-001.html`

https://github.com/servo/servo/actions/runs/28233372997/job/83643843817

```
  ▶ OK /css/css-animations/animation-iteration-event-001.html
  └   ▶ PASS [expected FAIL] Got the expected elapsedTime in the correct order
```

This is a test that I'm adding in #45990 to cover #45992. Seems it sometimes passes, I guess it's fine to leave it as intermittent until the bug gets fixed.