Undo double flush in example

ctru-rs/examples/gfx-3d-mode.rs

@@ -64,9 +64,6 @@ fn main() {
         left.flush_buffer();
         left.swap_buffers();
 
-        right.flush_buffer();
-        right.swap_buffers();
-
         //Wait for VBlank
         gfx.wait_for_vblank();
     }