Fixed a build error when including WinRT's SDLmain file directly in an app

src/main/winrt/SDL_winrt_main_NonXAML.cpp

@@ -1,7 +1,6 @@
 /*
     SDL_winrt_main_NonXAML.cpp, placed in the public domain by David Ludwig  3/13/14
 */
-#include "../../../SDL_internal.h"
 
 #include "SDL_main.h"
 #include <wrl.h>