SDL_offscreenwindow.c: swap include order of SDL_egl_c.h/SDL_sysvideo.h

Fixes redefinition warnings from windows builds.
Reference issue: https://github.com/libsdl-org/SDL/issues/6239

src/video/offscreen/SDL_offscreenwindow.c

@@ -22,8 +22,8 @@
 
 #if SDL_VIDEO_DRIVER_OFFSCREEN
 
-#include "../SDL_egl_c.h"
 #include "../SDL_sysvideo.h"
+#include "../SDL_egl_c.h"
 
 #include "SDL_offscreenwindow.h"