Rm go/v4 plugin note from OSDK upgrade

Author: adellape

modules/osdk-updating-v125-to-v128.adoc

@@ -33,13 +33,6 @@ endif::[]
 
 The following procedure updates an existing {type}-based Operator project for compatibility with {osdk_ver}.
 
-ifdef::golang[]
-[NOTE]
-====
-The `go/v3` plugin is being deprecated by Kubebuilder. As a result, the Operator SDK is planned to migrate to the `go/v4` plugin in a future release.
-====
-endif::[]
-
 .Prerequisites
 
 * Operator SDK {osdk_ver} installed