Doc Allow subgroups to use their parent group's custom project templates

Doc for "Allow a template in a namespace which is out of the
hierarchy of the Group owning the template"

doc/user/group/custom_project_templates.md

@@ -24,7 +24,7 @@ project in the group will be available to every logged in user.
 However, private projects will be available only if the user is a member of the project.
 
 NOTE: **Note:**
-Projects of nested subgroups of a selected template source cannot be used.
+Only direct subgroups can be set as the template source. Projects of nested subgroups of a selected template source cannot be used.
 
 Repository and database information that are copied over to each new project are
 identical to the data exported with [GitLab's Project Import/Export](../project/settings/import_export.md).