Update existing uses of /wd4267 to use the GN config

net/third_party/nss/ssl/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.
 
 config("ssl_config") {
   include_dirs = [ "." ]
 
   if (is_mac || is_win) {
     defines = [ "NSS_PLATFORM_CLIENT_AUTH" ]
   }
@@ skipping 52 matching lines @@
   defines = [
     "NO_PKCS11_BYPASS",
     "NSS_ENABLE_ECC",
     "USE_UTIL_DIRECTLY",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
 
   if (is_win) {
-    cflags += [ "/wd4267" ]  # Disable warning: Conversion from size_t to 'type'.
-
     sources -= [
       "unix_err.c",
       "unix_err.h",
     ]
     if (component_mode == "shared_library") {
       ldflags = [ "/DEF:" + rebase_path("exports_win.def", root_build_dir) ]
     }
   } else if (is_linux) {
     if (component_mode == "shared_library") {
       configs -= [ "//build/config/gcc:symbol_visibility_hidden" ]
@@ skipping 35 matching lines @@
     public_deps = [
       "//third_party/nss:nspr",
       "//third_party/nss:nss",
     ]
   }
 
   if (is_debug) {
     defines += [ "DEBUG" ]
   }
 }