replace include guards with pragma once

src/frontend/screens/Screen.hpp

@@ -1,5 +1,4 @@
-#ifndef FRONTEND_SCREENS_SCREEN_HPP_
-#define FRONTEND_SCREENS_SCREEN_HPP_
+#pragma once
 
 #include "util/ObjectsKeeper.hpp"
 
@@ -18,5 +17,3 @@ public:
     virtual void draw(float delta) = 0;
     virtual void onEngineShutdown() {};
 };
-
-#endif // FRONTEND_SCREENS_SCREEN_HPP_