doc: reword upgrade instructions (#348)

Updated version references for product documentation upgrade instructions.

Author: IceCodeNew

docs/en/upgrade/upgrade_global_cluster.mdx

@@ -98,7 +98,7 @@ Review the available component updates in the dialog, and confirm to proceed.
 The **Alauda Container Platform Product Docs** plugin provides access to product documentation within the platform. All help links throughout the platform will direct users to this documentation. If this plugin is not installed, clicking help links in the platform will result in 404 access errors.
 :::
 
-Starting from ACP 4.0, the built-in product documentation has been separated into the **Alauda Container Platform Product Docs** plugin. If you are upgrading from version 3.18, you need to install this plugin by following these steps:
+Starting from <Term name="productShort" /> 4.0, the built-in product documentation has been separated into the **Alauda Container Platform Product Docs** plugin. If you are upgrading from <Term name="productShort" /> 3.x, you need to install this plugin by following these steps:
 
 1. Navigate to **Administrator**.