Revert "nixos/fonts: Add unifont to list of default fonts."

This reverts commit 53746ff9d2 because
it increases default system closure size significantly. It's also
unnecessary - people can always add fonts themselves.

nixos/modules/config/fonts/fonts.nix

@@ -31,7 +31,6 @@ with lib;
         pkgs.xorg.fontbh100dpi
         pkgs.xorg.fontmiscmisc
         pkgs.xorg.fontcursormisc
-        pkgs.unifont
       ];
 
   };