Spurious test failures in ChatListRenderer.fireItemHeightChange

https://github.com/microsoft/vscode/actions/runs/30125958708/job/89589396846?pr=327391
(https://github.com/microsoft/vscode/pull/327391)
https://github.com/microsoft/vscode/actions/runs/30128189422/job/89597727903?pr=327248

```
1) ChatListRenderer
fireItemHeightChange defers a mid-render measurement and delivers it after the render pass:

+ expected - actual

{
"events": [
- 86
+ 114
]
- "stored": 86
+ "stored": 114
}

AssertionError [ERR_ASSERTION]: Expected values to be strictly deep-equal:
+ actual - expected

{
events: [
+ 86
- 114
],
+ stored: 86
- stored: 114
}

at Context. (file:///Users/runner/work/vscode/vscode/out/vs/workbench/contrib/chat/test/browser/widget/chatListRenderer.test.js:564:12)
```