There is no “management UI” for those. There’s an API endpoint but its usage is fraught with peril, so instead, please read this article:
and based on its advice, figure out what you’ll need (either changing submodules to public so you have at most 0 private submodules,or instead creating a “dummy” user to hold the deploy key as an access key), and let us know what decision you come to - if we end up creating a new key for you builds will IMMEDIATELY stop working until you replace with the one we’ve made - and we’ll help out and generate a new key for you.