Now that the underlying bug is fixed, we can expect the test to always
pass.

Also simplify the test a tiny bit and skip it on debug builds because
it's slow.

Bug: chromium:1161357
Change-Id: I2ce5e064b4f707f4bd680f04df95d5a342bec1b0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2616220Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71972}