I originally marked AllocationMemento::allocation_site as @noVerifier
out of an abundance of caution because AllocationMemento::IsValid checks
whether allocation_site is an AllocationSite. However, I can't find any
way for allocation_site to not be an AllocationSite.

Bug: v8:9311
Change-Id: I8b7ab51978c90d9baff42dace28d176a1cd2921a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1653520Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#62120}