Change default `freezePrototype` to false, closes #3416 #3406

Editor assessment

The subject states the default change exactly: freezePrototype now defaults to false, with two issues cited. Type fix and scope core are accurate, and the exact flag name makes the change verifiable. A body explaining the security trade-off of disabling prototype freezing would have taught something real, but the headline states the actionable fact and the issues carry the reasoning. No footers beyond the PR number. Precise and complete, slightly under-explained.