Re-enable warning 4005 and remove _CRT_SECURE_NO_WARNINGS

The macro _CRT_SECURE_NO_WARNINGS is no longer needed for chromium
code as pdfium code itself is warning free;
For standalone build, the macro may suppress warnings from third
party code. But it has no use now as it is shadowed by disabled 4996
warnings.

This is one of the efforts to re-enable warnings for pdfium code.

BUG=pdfium:29
R=brucedawson@chromium.org

Review URL: https://codereview.chromium.org/1836443002 .

1 files changed, 0 insertions, 1 deletions

diff --git a/BUILD.gn b/BUILD.gn
index f22a418b99..a21c0da263 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -18,7 +18,6 @@ config("pdfium_config") {
     "PNG_PREFIX",
     "PNG_USE_READ_MACROS",
     "V8_DEPRECATION_WARNINGS",
-    "_CRT_SECURE_NO_WARNINGS",
   ]
 
   if (pdf_use_skia) {