winrt: Removed WinRT/Windows Phone/UWP support.

Fixes #10724.

src/core/windows/SDL_windows.h

@@ -122,10 +122,8 @@ extern bool WIN_SetErrorFromHRESULT(const char *prefix, HRESULT hr);
 // Sets an error message based on GetLastError(). Always return -1.
 extern bool WIN_SetError(const char *prefix);
 
-#ifndef SDL_PLATFORM_WINRT
 // Load a function from combase.dll
 FARPROC WIN_LoadComBaseFunction(const char *name);
-#endif
 
 // Wrap up the oddities of CoInitialize() into a common function.
 extern HRESULT WIN_CoInitialize(void);