Removing redundant header

(cherry picked from commit 74c30545031ca8cdb69b2f1ec173e77d79078093)

extras/physfssdl3.c

@@ -24,7 +24,6 @@
 /* This works with SDL3. For SDL1 and SDL2, use physfsrwops.h */
 
 #include "physfssdl3.h"
-#include "SDL3/SDL_iostream.h"
 
 /* SDL_IOStream -> PhysicsFS bridge ... */