chore: Update changelog date for version 1.20.2

Author: harshithad0703

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-## [v1.20.2](https://github.com/contentstack/contentstack-management-javascript/tree/v1.20.2) (2025-04-14)
+## [v1.20.2](https://github.com/contentstack/contentstack-management-javascript/tree/v1.20.2) (2025-04-21)
  - Fix
     - Handle the sanity tests when ENVs are not provided
 ## [v1.20.1](https://github.com/contentstack/contentstack-management-javascript/tree/v1.20.1) (2025-04-07)