Also remove the out of date comment after constant pool enabled.

Change-Id: I80ded0242406097dfdb35e1356ed8fa7e43b2f00
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2839546Reviewed-by: Brice Dobry <brice.dobry@futurewei.com>
Commit-Queue: Brice Dobry <brice.dobry@futurewei.com>
Cr-Commit-Position: refs/heads/master@{#74409}