Two tests already test concurrent allocation. Another one measures
memory, so non-deterministic allocation would lead to higher memory
usage than anticipated.

Bug: v8:10315
Change-Id: If994233c87ea04076b850ffdf024f7783653e9db
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2352781Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69383}