This type is no longer required: all ExternalPointers are now
sandboxified in turbofan, so we use that type instead.

Bug: v8:10391
Change-Id: Ia2bd261bfe3cfd5c7d9c350ba0e553e57a596a42
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/+/3359632Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78802}