Let me make sure you are routed to the right support that can help you remove the smart vault option in your QuickBooks Online (QBO).
Since SmartVault is a third party application, I recommend you get in touch with the SmartVault technical support. They'll be able to help you remove the smart vault icon from your QBO account. You can visit their website to get their contact information.
Stay in touch with me if there's anything I can help you with. I'll be around in the Community.