In the Forms module, admins have the ability to toggle double email verification on/off.
From the blue admin bar, hover over the "Full Settings List" option and select it
From the full settings list, scroll down until you come to the Forms section:
Select "One Email Field" and you'll be taken to the Forms-specific settings list.
Click on the "One Email Field" dropdown option and select "true".
This will disable double email verification and transform forms from this view:
to the single email field view: