GraphicsMagick is a replacement for ImageMagick. Now sys-apps/paludis depends only on media-gfx/imagemagick.
Sorry about the mass reassignment, but this undertaking really shouldn't burden bug-wranglers further.
Well, I haven't been able to find where ImageMagick is used there. Moreover, the docs build fine and seem to give the same result without imagemagick installed. Therefore, I have removed the imagemagick dep completely.