UnsafePointerAdd is unnecessary as long as a proper bitcast is used
before the addition. The bitcast is already in the effect chain and
prevents the addition from floating before a GC operation.

Change-Id: Ieadb8a51d2d24eaa1132a62c77c674954f7e2644
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3616727Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80457}