You can revoke’s access to your Dropbox account by navigating to Dropbox Settings in your Web Browser and scrolling down to the 'Apps with access to your Dropbox' section. Find and press the (X) next to it, displaying the option to ‘Disconnect’

Should you want to reconnect to your libraries after this, simply login to your Dropbox in the app. However, please note that if you select ‘Also remove the folder from my Dropbox', any remaining libraries will be deleted.