Since implicit returns are gone, this environment is never being used.

R=titzer@chromium.org

Bug: v8:8423
Change-Id: I24d61a1316433fde6835fd608c3d308592721a5c
Reviewed-on: https://chromium-review.googlesource.com/c/1371569
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58155}