The MustHaveMenus Facebook Menu Tab is no longer supported. You can remove the 'Menu' tab itself with the instructions below:
Login into your Facebook account and visit your Facebook business page. In the upper right of your business page, click on "Settings." From the Settings page, in the left column, click on "Templates and Tabs."
On the Templates and Tabs page, under the "Home" tab (center column), locate the "Menu" tab. Click on the "Settings" button.
The control for displaying the "Menu" tab will now be exposed. Click the toggle button to "Off" and then click the "Save" button. The "Menu" tab will no longer appear on your business page.