Remove MinGW specific value of _WIN32_WINNT

For historical reasons MinGW used to define a higher value for
_WIN32_WINNT. Over years of refactoring this turned into a _lower_
value, which has then started breaking compilation on MinGW. This
change gets ride of the MinGW specific value.

R: mlippautz@chromium.org
Bug: V8:12099
Change-Id: Ic24b71c6767cd4d1b53a6cb6487517dec614cd1a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3123639Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76545}

src/base/win32-headers.h

@@ -41,12 +41,6 @@
 
 #include <signal.h>  // For raise().
 #include <time.h>  // For LocalOffset() implementation.
-#ifdef __MINGW32__
-// Require Windows XP or higher when compiling with MinGW. This is for MinGW
-// header files to expose getaddrinfo.
-#undef _WIN32_WINNT
-#define _WIN32_WINNT 0x501
-#endif  // __MINGW32__
 #if !defined(__MINGW32__) || defined(__MINGW64_VERSION_MAJOR)
 #include <errno.h>           // For STRUNCATE
 #endif  // !defined(__MINGW32__) || defined(__MINGW64_VERSION_MAJOR)