docs: update v6.0.0 release date to April 5, 2026 (#134)

Author: saurabhjain1592

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to the AxonFlow Python SDK 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).
 
-## [6.0.0] - 2026-04-04
+## [6.0.0] - 2026-04-05
 
 ### BREAKING CHANGES