`test/issue-3356.js` very flaky when run with test runner

[targos]

Reproduce with npm run test:unit. It almost fails every time on my machine (MacBook M2 Pro).
This makes undici fail CITGM runs.

[targos]

Failure is a timeout:

✖ test/issue-3356.js (30002.591792ms)
  'test timed out after 30000ms'

[mcollina]

I think we should skip this in citgm (when process.env.CITGM is set).

That specific test has been flaky even here, I guess there might be something to investigate.

[mcollina]

Tagged good first issue for skipping

[targos]

It's not specific to citgm. It fails very consistently on my own machine, just by running npm run test:unit

[targos]

Note that it only times out if run with other tests. I cannot reproduce by running node test/issue-3356.js directly.