The test takes several minutes on slower bots, so speed it up a bit
without removing the ability to hit the data race.

R=ulan@chromium.org

Bug: chromium:1205290, v8:11741
Change-Id: I57e411bfa2ff2a22bef1a916b74f7684b2f0be17
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2876855Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74408}