If you have previously connected your Google Drive to your account and would like to undo this, you have two options:
Log into your account, go to the “My Info” page, and deselect the option for connecting your Google Drive to your account in the “Google Account” section.
Stop the Proofed app from accessing your Google Drive via your Google Drive account. Google has a helpful article here (you will find the relevant instructions under “Remove site or app access”) explaining exactly how to do this.