How to remove Private Metafield from a client's store after uninstalling an app?

Our client has reported encountering difficulties after uninstalling our app, Webrex Announcement Bar. Despite the uninstallation, remnants of our code are persisting in their store. After a thorough investigation, we have identified a specific issue with the Private Metafield.

Merchant shop URL - https://wolph.co.uk/

To resolve this, we kindly request that you remove the Private Metafield associated with our app from the client’s Shopify store. This will ensure a clean and seamless experience for them.

Merchant current theme -

Speed - Venture - V2.2