It turns out we can just remove kReturnVariable from the normal change
tracking, since it's always set when jumping to the final label anyway.

Bug: v8:7793
Change-Id: I6d0a777016047aa31b0edddd19c661e2631e1078
Reviewed-on: https://chromium-review.googlesource.com/1124471Reviewed-by: Daniel Clifford <danno@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54171}