untrunc-anthwlock: mark as unbroken on darwin

Fixed by c39770ecc54 (libui: fix typo when installing libs on darwin,
2022-07-09).

pkgs/tools/video/untrunc-anthwlock/default.nix

···
   enableParallelBuilding = true;
 
   meta = with lib; {
-    broken = stdenv.isDarwin;
     description = "Restore a truncated mp4/mov (improved version of ponchio/untrunc)";
     homepage = "https://github.com/anthwlock/untrunc";
     license = licenses.gpl2;