Style: Replace header guards with #pragma once

tests/scene/test_timer.h

@@ -28,8 +28,7 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
 /**************************************************************************/
 
-#ifndef TEST_TIMER_H
-#define TEST_TIMER_H
+#pragma once
 
 #include "scene/main/timer.h"
 
@@ -213,5 +212,3 @@ TEST_CASE("[SceneTree][Timer] Check Timer timeout signal") {
 }
 
 } // namespace TestTimer
-
-#endif // TEST_TIMER_H