Replace include guards with pragma once

examples/PoolBox/application/src/assets.hpp

@@ -1,5 +1,4 @@
-#ifndef __ASSETS_HPP__
-#define __ASSETS_HPP__
+#pragma once
 #include <PSX/File/Processor/cd_file_processor.hpp>
 
 namespace Assets {
@@ -7,6 +6,4 @@ namespace Assets {
 
     static constexpr auto FontTIM = SimpleTIM(960, 0, 960, 511);
     void load_for_main();
-}
-
-#endif //!__ASSETS_HPP__
+}