Remove stale mentions of mandoline.

.gn

 # This file is used by the GN meta build system to find the root of the source
 # tree and to set startup options. For documentation on the values set in this
 # file, run "gn help dotfile" at the command line.
 
 # The location of the build configuration file.
 buildconfig = "//build/config/BUILDCONFIG.gn"
 
 # The secondary source root is a parallel directory tree where
 # GN build files are placed when they can not be placed directly
 # in the source tree, e.g. for third party source trees.
@@ skipping 39 matching lines @@
   "//google_apis/*",
   "//google_update/*",
 
   #"//gpu/*",  # Lots of errors.
   "//gpu:*",
 
   #"//ios/*",
   "//ipc/*",
 
   #"//jingle/*",
-  "//mandoline/*",
   "//mash/*",
 
   #"//media/*",  # Lots of errors.
   "mojo/*",
 
   #"//native_client/*",
   #"//net/*",  # Needs GN binary changes to work on Android.
 
   #"//pdf/*",  # Medium-hard.
   #"//ppapi/*",  # Lots of errors.
@@ skipping 160 matching lines @@
   "//tools/gn/format_test_data/055.golden",
   "//tools/gn/function_exec_script.cc",
   "//tools/gn/gn.gyp",
   "//tools/gn/input_conversion.cc",
   "//tools/gn/misc/emacs/gn.el",
   "//tools/gn/misc/vim/syntax/gn.vim",
   "//tools/gn/setup.cc",
   "//ui/accessibility/BUILD.gn",
   "//ui/views/BUILD.gn",
 ]