Revert "Fix mujs dylib on Darwin"

mujs already fixes its dylib.

This reverts commit a1abee0758440a5ba542f1f1466792b6b78a5739.

pkgs/applications/video/mpv/default.nix

···
   # See the explanation in addOpenGLRunpath.
   postFixup = lib.optionalString stdenv.isLinux ''
     addOpenGLRunpath $out/bin/mpv
-  '' + lib.optionalString (stdenv.isDarwin && javascriptSupport) ''
-    ${stdenv.cc.targetPrefix}install_name_tool -change "build/release/libmujs.dylib" \
-      "${mujs}/lib/libmujs.dylib" $out/bin/mpv
   '';
 
   passthru = {