We don't have the ability to completely remove a logo from the design page - however you can get around this by uploading a transparent PNG with a single pixel coloured in - its so small its almost non existent.
You can download this here
It looks like there is nothing there, but right click and select "Save image as" to save the 1px image. It will be called "Pixel".
Then simply upload this image as your +Choose Logo on the Design page: