How to delete Macbook from Find My iPhone without erasing data?
In Find iPhone you should be able to tap on the device you want to remove. That will take you to the screen where you see the Erase option. 

At the top-right of that screen is the option to Remove that device (see my iPad screenshot below). 



If the Remove option doesn't appear immediately, give it a few minutes to show up. After tapping Remove you'll get a confirmation dialog box. Once you tap Agree the device will be removed.