It was in one of the 10.3 betas but was removed. I don't think it can be deleted reliably without losing data if iCloud keychain is enabled, e.g. another device

It was in one of the 10.3 betas but was removed. I don't think it can be deleted reliably without losing data if iCloud keychain is enabled, e.g. another device might still have the same app or share the app group.