test: mark connection leak test flaky on IBM i
Mark test-http-pipeline-requests-connection-leak
flaky on IBM i.
Refs: https://github.com/nodejs/node/issues/43509 Refs: https://github.com/nodejs/node/issues/39683
There's an underlying issue on IBM i for which an OS patches (PTFs) are available but we've not been able to get them applied onto all of the IBM i machines we have in the CI.