CHANGELOG: update release date

Signed-off-by: Gyuho Lee <leegyuho@amazon.com>

Author: gyuho

CHANGELOG/CHANGELOG-1.4.md

@@ -3,7 +3,7 @@
 <hr>
 
 
-## [v1.4.0](https://github.com/aws/aws-k8s-tester/releases/tag/v1.4.0) (2020-06-28)
+## [v1.4.0](https://github.com/aws/aws-k8s-tester/releases/tag/v1.4.0) (2020-06-29)
 
 See [code changes](https://github.com/aws/aws-k8s-tester/compare/v1.3.9...v1.4.0).