Style: Replace header guards with #pragma once

scene/gui/graph_element.h

@@ -28,8 +28,7 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
 /**************************************************************************/
 
-#ifndef GRAPH_ELEMENT_H
-#define GRAPH_ELEMENT_H
+#pragma once
 
 #include "scene/gui/container.h"
 
@@ -93,5 +92,3 @@ public:
 
 	GraphElement() {}
 };
-
-#endif // GRAPH_ELEMENT_H