By disengaging it from 'let' which is not implemented in liftoff yet.

Bug: v8:7748
Change-Id: I191695767bf8c6153f70d509dd13ff734fe75e01
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2676631Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72620}