This allows GC to go slightly over the max heap limit in order to give
NearHeapLimitCallback a chance to run and increase the limit.

Based on the suggestion by Kenton Varda.

Change-Id: I9c084b5a4c8fb7b9ce331b565958391c1be56add
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2505724
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70884}