Update CHANGELOG.md for v3.0 (#6424)

CHANGELOG.md

@@ -8,12 +8,15 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 and follows a [Backwards Compatibility Policy](https://docs.solanalabs.com/backwards-compatibility)
 
 Release channels have their own copy of this changelog:
-* [edge - v2.3](#edge-channel)
-* [beta - v2.2](https://github.com/anza-xyz/agave/blob/v2.2/CHANGELOG.md)
-* [stable - v2.1](https://github.com/anza-xyz/agave/blob/v2.1/CHANGELOG.md)
+* [edge - v3.0](#edge-channel)
+* [beta - v2.3](https://github.com/anza-xyz/agave/blob/v2.3/CHANGELOG.md)
+* [stable - v2.2](https://github.com/anza-xyz/agave/blob/v2.2/CHANGELOG.md)
 
 <a name="edge-channel"></a>
-## 2.3.0 - Unreleased
+## 3.0.0 - Unreleased
+
+
+## 2.3.0
 
 ### Validator