desktop-files-utils: add setupHook to remove mimeinfo.cache

Post-Installation scripts are running `update-desktop-database -q`
creating these files which obviously results in a lot of collisions.

Much better solution than eventually noticing their existence and
removing them in postInstall.

pkgs/development/tools/profiling/sysprof/default.nix

@@ -46,10 +46,6 @@ in stdenv.mkDerivation rec {
     "-Dsystemdunitdir=lib/systemd/system"
   ];
 
-  postInstall = ''
-    rm $out/share/applications/mimeinfo.cache
-  '';
-
   passthru = {
     updateScript = gnome3.updateScript {
       packageName = pname;