[turbofan] make constant fold comments more readable

Change-Id: I5e31bbce2bfbf0effa2c660a67ec88bcd49d06a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2335054
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69199}