Update CHANGELOG.md

Author: zHaytam

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## Diagrams (3.0.0-preview.2) - 2022-09-11
+## Diagrams (3.0.0-beta.2) - 2022-09-11
 
 ### Added
 
@@ -28,7 +28,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - `EnableVirtualization` option (see added alternative)
 
-## Diagrams (3.0.0-preview.1) - 2022-09-04
+## Diagrams (3.0.0-beta.1) - 2022-09-04
 
 .NET 6!