The test was not flaky. Instead it seems compiiler optimizations discarded
of the test-allocated object such that stack scanning could no longer find it.

Bug: v8:11052
Change-Id: Ie8018ccecb03b22e6c4f2dada3e6663b04c551fd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2493160
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70722}