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. Follow the easy steps mentioned below.
Step 1: Click on ACTIONS on the form from which you want to remove the Mailmunch logo. Select the Edit option from the drop-down menu.
Step 2: Open the Appearance tab, and expand the MailMunch Logo panel.
Step 3: Switch on the REMOVE MAILMUNCH LOGO toggle.
You can find more about different plans and features covered under them on MailMunch Pricing page.