Update CHANGELOG.md

Update release date.

Author: josipk-ib

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to the library will be documented in this file.
 The format of the file is based on [Keep a Changelog](http://keepachangelog.com/)
 and this library adheres to [Semantic Versioning](http://semver.org/) as mentioned in [README.md][readme] file.
 
-## [ [2.0.0](https://github.com/infobip/infobip-api-csharp-client/releases/tag/2.0.0) ] - 2021-05-07
+## [ [2.0.0](https://github.com/infobip/infobip-api-csharp-client/releases/tag/2.0.0) ] - 2021-05-11
 
 🎉 **NEW Major Version of `Infobip.Api.Client`.**