update CHANGELOG.md

Author: ayodeko

CHANGELOG.md

@@ -27,6 +27,7 @@ All notable changes to this project will be documented in this file.
 - Updated the default value of the `all` attribute in the `ports` Syscollector configuration option. ([#8840](https://github.com/wazuh/wazuh-documentation/pull/8840))
 - Replaced version references with replacement variables in Wazuh package generation. ([#8906](https://github.com/wazuh/wazuh-documentation/pull/8906))
 - Updated System inventory documentation. ([#8910](https://github.com/wazuh/wazuh-documentation/pull/8910))
+- **Post-release**: Updated steps in Upgrade Guide for exporting customizations from the Wazuh Dashboard. ([#8921](https://github.com/wazuh/wazuh-documentation/pull/8921))
 
 ## [v4.12.0]