Remove unused variable reported by gcc.

Change-Id: I02b37a41524d2c2d8e3ab1158bd0fd816c7124f1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3629601Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80387}