This is no longer needed as all backing store allocations must now be
located inside the sandbox after sandboxed pointers were enabled by
default when the sandbox is enabled.

Bug: chromium:1218005
Change-Id: Id2d5feba878e1a6a5775ae3fef4012d0e7fe667a
Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng,v8_linux_arm64_sim_heap_sandbox_dbg_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3738742Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81488}