Updating CHANGELOG

[aaronjeline]

Description of changes

We decided to include #1180 in 4.0, so this updates the changelog

Issue #, if available

N/A

Checklist for requesting a review

The change in this PR is (choose one, and delete the other options):

• [X] A change "invisible" to users (e.g., documentation, changes to "internal" crates like cedar-policy-core, cedar-validator, etc.)