how to remove a menu item under product detail page "Promote" menu that come with an app

[feng2]

in this following image, this is the product detail page. you can see there is "Promote" menu with dropdown menu "Feature on order  confirmation" . we want to remove this menu. but we can't find any where to remove this in our app.

We know under App setting, there is "extension" setting, where you can create "admin link" extension to add extra menu item under "more actions" menu. 

but in our app, the "extension" setting is empty. there is nothing for us to delete. 

we have asked coworker who worked on this feature, he mentioned that was created by an old setting(because current extension setting can only out extra menu under "more actions" but not "promote"
Please tell us how we can remove this "Promote" menu within our app