Drop Windows XP support remnants

libavcodec/dxva2_mpeg2.c

@@ -21,14 +21,11 @@
  */
 
 #include "libavutil/log.h"
+
+#include "dxva2_internal.h"
 #include "mpegutils.h"
 #include "mpegvideo.h"
 
-// The headers above may include w32threads.h, which uses the original
-// _WIN32_WINNT define, while dxva2_internal.h redefines it to target a
-// potentially newer version.
-#include "dxva2_internal.h"
-
 #define MAX_SLICES 1024
 struct dxva2_picture_context {
     DXVA_PictureParameters pp;