modules/config/fonts.nix: revert "export GDFONTPATH in /etc/profile"

This reverts commit 2802538dc2. The idea
was good, but unfortunately $GDFONTPATH has a different format, i.e.
programs that use this variable don't descend into the directories
listed here like fontconfig does, so we cannot use the same values for
both settings.

modules/config/fonts.nix

@@ -171,7 +171,6 @@ in
   environment.shellInit =
     ''
       export FONTCONFIG_FILE=/etc/fonts/fonts.conf
-      export GDFONTPATH=${concatStringsSep ":" config.fonts.fonts}
     '';
 
   environment.systemPackages =