Everything after UNREACHABLE is dead code, so it makes sense to remove them.

Bug: v8:9183
Change-Id: If76468a73b926d74717cc2348fd5b36d30f680c1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1605727Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61411}