The Arial font gets included by default and cannot be removed. However it can be reduced in size.
In the Assets → Fonts tab in the Luna plugin window. Change the ‘default font settings’ to reduce the texture size down to 32x32 and the glyph size to 1. This will override the default settings.
If a separate font is being used and requires higher resolution. In the ‘Per font settings' area. Select the font, and set its texture and glyph size to a larger value.