This adds a comment to explain why the additional "ret" instruction
added in https://crrev.com/c/3071202 is actually needed.

R=mseaborn@chromium.org
CC=ahaas@chromium.org

Bug: v8:11955
Change-Id: Ifd874c499fd3094f7cf5383e991d6b193b23ca63
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3081601Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76230}