This reverts commit 4f4b4f74.

Reason for revert: New unittest is failing on TSAN bot:

https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20TSAN%20-%20stress-incremental-marking/3210

Original change's description:
> cppgc-js: Add unittest for CollectCustomSpaceStatisticsAtLastGC
>
> Drive-by: fix delayed task implementation in cpp-heap.cc.
>
> Bug: chromium:1056170
> Change-Id: Ie92d909056532047b378ebfafeb98273997e60e9
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2883618
> Commit-Queue: Omer Katz <omerkatz@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74530}

Bug: chromium:1056170
Change-Id: I7e50f20178854081b6fd23aa6d31afc4b9e49850
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2891462
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74540}