📖 Fix: broken url in extending_cli_features_and_plugins.md (#4341)

You can see the current 404 here: https://book.kubebuilder.io/plugins/extending/extending_cli_features_and_plugins#plugin-keys

(after clicking on go the kubebuilder.io URL)

Author: monteiro-renato

docs/book/src/plugins/extending/extending_cli_features_and_plugins.md

@@ -406,7 +406,7 @@ creating features or plugins that can rely on this information.
 [kb-utils]: https://github.com/kubernetes-sigs/kubebuilder/blob/book-v4/pkg/plugin/util/util.go
 [project-file-config]: ./../../reference/project-config.md
 [cli]: ./../../../../../pkg/cli
-[kb-go-plugin]: ./../../../../../pkg/plugins/golang/v4
+[kb-go-plugin]: https://github.com/kubernetes-sigs/kubebuilder/tree/book-v4/pkg/plugins/golang/v4
 [cobra]: https://github.com/spf13/cobra
 [external-plugin]: external-plugins.md
 [deploy-image]: ./../available/deploy-image-plugin-v1-alpha.md