fontconfig: get rid of rest of versioned configs

The incompatibility does not seem to exist any more: programs linked against fc 2.12
on fc 2.14 system seem to at least display text, even while printing tons of errors
(as long as you generate fc cache manually), and same thing the other way around.
Hopefully it will not be an issue in the future.

nixos/modules/config/fonts/fontconfig.nix

@@ -1,6 +1,6 @@
 /*
 
-Configuration files are linked to /etc/fonts/${pkgs.fontconfig.configVersion}/conf.d/
+Configuration files are linked to /etc/fonts/conf.d/
 
 This module generates a package containing configuration files and link it in /etc/fonts.
 
@@ -176,15 +176,16 @@ let
   confPkg = pkgs.runCommand "fontconfig-conf" {
     preferLocalBuild = true;
   } ''
-    dst=$out/etc/fonts/${pkg.configVersion}/conf.d
+    dst=$out/etc/fonts/conf.d
     mkdir -p $dst
 
     # fonts.conf
     ln -s ${pkg.out}/etc/fonts/fonts.conf \
           $dst/../fonts.conf
     # TODO: remove this legacy symlink once people stop using packages built before #95358 was merged
-    ln -s /etc/fonts/${pkg.configVersion}/fonts.conf \
-          $out/etc/fonts/fonts.conf
+    mkdir -p $out/etc/fonts/2.11
+    ln -s /etc/fonts/fonts.conf \
+          $out/etc/fonts/2.11/fonts.conf
 
     # fontconfig default config files
     ln -s ${pkg.out}/etc/fonts/conf.d/*.conf \