NewSpace shrinking is already performed in Heap::GarbageCollectionEpilogueInSafepoint.

Bug: chromium:1054771
Change-Id: Ia274dd5619fd1d7397a06f0b642f07d68de45ea1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2563267
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71451}