This article explains how to remove Form Publisher from your Google account.
If you want to remove the add-on from a Google Form, you will have to remove the add-on from the G Suite Marketplace.
From your Google account, click on the menu at the top left side. Then, click ‘More from G Suite Marketplace’:
The G Suite Marketplace page opens. You can either click on ‘Manage Apps’ > ‘Uninstall’:
Or click ‘Uninstall’ directly from Form Publisher add-on:
A pop-up appears asking if you want to confirm to 'Uninstall app'.
That’s it! If you check on a Google Form you will see that Form Publisher has been correctly uninstalled: