Set 4.6.0 release date in changelog (#1877)

Author: john-h-kastner-aws

cedar-policy/CHANGELOG.md

@@ -12,7 +12,7 @@ Starting with version 3.2.4, changes marked with a star (*) are _language breaki
 
 ## Unreleased
 
-## [4.6.0] - Coming Soon
+## [4.6.0] - 2025-10-06
 
 Cedar Language Version: 4.4