Remove GYP annotations from third_party GN files.

third_party/libjingle/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/features.gni")
 
-# From third_party/libjingle/libjingle.gyp's target_defaults.
 config("jingle_unexported_configs") {
   include_dirs = [
     "../../third_party/webrtc_overrides",
     "../../testing/gtest/include",
     "../../third_party",
     "../../third_party/libyuv/include",
     "../../third_party/usrsctp/usrsctplib",
   ]
 }
 
-# From third_party/libjingle/libjingle.gyp's target_defaults.
 config("jingle_public_configs") {
   include_dirs = [
     "../../third_party/webrtc_overrides",
     "../../testing/gtest/include",
     "../../third_party",
   ]
 }
 
-# From third_party/libjingle/libjingle.gyp's target_defaults.
 group("jingle_deps") {
   public_deps = [
     "//third_party/expat",
   ]
   deps = [
     "//base",
     "//crypto:platform",
     "//net",
   ]
 }
 
-# GYP version: third_party/libjingle.gyp:libjingle
 static_library("libjingle") {
   # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   public_deps = [
     ":jingle_deps",
 
     # TODO(kjellander): Start cleaning up this target as soon as
     # https://codereview.chromium.org/2022833002/ is landed. The target should
     # be removed entirely if possible.
@@ skipping 83 matching lines @@
     sources = [
       "$p2p_dir/stunprober/stunprober.cc",
     ]
 
     deps = [
       ":libjingle_webrtc_common",
       "//third_party/webrtc/base:rtc_base",
     ]
   }
 }  # enable_webrtc