The feature is controlled by a boolean flag on Isolate, so there's no
need to keep the flag read-only.

Bug: v8:11527, chromium:1241665
Change-Id: I377452fed10b319a4a512c090706c754603c2ae8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3270547
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77820}