You could unplug it if your objection is to having the hardware there if you are not using it. However, you might then get a "DF0:

?" icon on your Workbench. You can disable this in OS3.9 (and 3.5?).
Alternatively, I have just found
this on Aminet, which says you can disable the floppy drive. Since it's in hard/hack I assume it is a hardware hack to physically disable DF0. I haven't looked in the archive or tried this, so I'm not making any promises it will do what you want :-)
--
moto