Currently background thread cannot allocate embedder objects and
checking the embedder heap size is not thread-safe. For simplicity,
we can skip the check until concurrent allocation of embedder objects
is supported.

Bug: chromium:1162744, chromium:1160097
Change-Id: I47d6299e77b986e4b2cb8da841e0149ef577918a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2640477Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72204}