Remove GN GYP generator.

tools/gn/secondary/components/translate/BUILD.gn

 # Copyright 2013 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.
 
 static_library("translate_core_browser") {
-  external = true
-
   sources = [
     "core/browser/language_state.cc",
     "core/browser/language_state.h",
     "core/browser/page_translated_details.h",
     "core/browser/translate_accept_languages.cc",
     "core/browser/translate_accept_languages.h",
     "core/browser/translate_browser_metrics.cc",
     "core/browser/translate_browser_metrics.h",
     "core/browser/translate_client.h",
     "core/browser/translate_download_manager.cc",
@@ skipping 15 matching lines @@
   ]
 
   deps = [
     ":translate_core_common",
     "//base",
     "//url",
   ]
 }
 
 static_library("translate_core_common") {
-  external = true
-
   sources = [
     "core/common/language_detection_details.cc",
     "core/common/language_detection_details.h",
     "core/common/translate_constants.cc",
     "core/common/translate_constants.h",
     "core/common/translate_errors.h",
     "core/common/translate_metrics.cc",
     "core/common/translate_metrics.h",
     "core/common/translate_pref_names.cc",
     "core/common/translate_pref_names.h",
     "core/common/translate_switches.cc",
     "core/common/translate_switches.h",
     "core/common/translate_util.cc",
     "core/common/translate_util.h",
   ]
 
   deps = [
     "//base",
     "//url",
   ]
 }