tools/gn: delete generate_test_gn_data tool

tools/gn/BUILD.gn

 # Copyright (c) 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.
 
 import("//testing/test.gni")
 
 defines = [ "GN_BUILD" ]
 
 static_library("gn_lib") {
   configs += [ "//build/config:precompiled_headers" ]
@@ skipping 294 matching lines @@
     "format_test_data/",
   ]
 
   deps = [
     ":gn_lib",
     "//base/test:run_all_unittests",
     "//base/test:test_support",
     "//testing/gtest",
   ]
 }
-
-executable("generate_test_gn_data") {
-  sources = [
-    "generate_test_gn_data.cc",
-  ]
-  deps = [
-    "//base",
-    "//build/config/sanitizers:deps",
-  ]
-}