Remove obsolete workaround for Qt4 (#7590)

src/core/main.cpp

@@ -367,10 +367,6 @@ int main( int argc, char * * argv )
 		printf( "LMMS cannot be run as root.\nUse \"--allowroot\" to override.\n\n" );
 		return EXIT_FAILURE;
 	}
-#endif
-#ifdef LMMS_BUILD_LINUX
-	// don't let OS steal the menu bar. FIXME: only effective on Qt4
-	QCoreApplication::setAttribute( Qt::AA_DontUseNativeMenuBar );
 #endif
 	QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
 	QCoreApplication * app = coreOnly ?