Also remove unused Factory::CopyFeedbackVector().

Bug: v8:7703
Change-Id: I75e16a55967e5970e4cbe3babae3a09d2a647313
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1611542Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61512}