corefonts: fix build

pkgs/data/fonts/corefonts/default.nix

···
   version = "1";
 
   exes = map ({name, sha256}: fetchurl {
-    url = "mirror://sourceforge/corefonts/${name}32.exe";
+    url = "mirror://sourceforge/corefonts/the%20fonts/final/${name}32.exe";
     inherit sha256;
   }) fonts;