This is a feature covered under premium MailMunch plans. If you have an upgraded premium MailMunch plan then you can disable MailMunch logo in the Appearance step of the form.
- Go to edit the form you want to remove the logo for
- Open the "Appearance" tab and expand the "MailMunch Logo" panel
- Turn the "Remove MailMunch Logo" toggle ON
You can find more about different plans and features covered under them on MailMunch Pricing page.