windowsrawinput: Add missing WIN_SetRawKeyboardFlag_Inputsink stub.

(cherry picked from commit 00f9a2587975d0fcf9508e5083dd79116e9f4f8d)

src/video/windows/SDL_windowsrawinput.c

@@ -323,6 +323,11 @@ bool WIN_SetRawKeyboardFlag_NoHotkeys(SDL_VideoDevice *_this, bool enabled)
     return SDL_Unsupported();
 }
 
+bool WIN_SetRawKeyboardFlag_Inputsink(SDL_VideoDevice *_this, bool enabled)
+{
+    return SDL_Unsupported();
+}
+
 #endif // !SDL_PLATFORM_XBOXONE && !SDL_PLATFORM_XBOXSERIES
 
 #endif // SDL_VIDEO_DRIVER_WINDOWS