ui: Move to pragma once

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

src/ui/linechart/Scrollbar.h

-#ifndef _SCROLLBAR_H
-#define _SCROLLBAR_H 1
+#pragma once
 
 #include <qscrollbar.h>
 
@@ -49,5 +48,3 @@ private:
     double d_maxBase;
     int d_baseTicks;
 };
-
-#endif

src/ui/uas/QGCUnconnectedInfoWidget.h

-#ifndef QGCUNCONNECTEDINFOWIDGET_H
-#define QGCUNCONNECTEDINFOWIDGET_H
+#pragma once
 
 #include <QWidget>
 
@@ -35,4 +34,3 @@ public slots:
     void addLink();
 };
 
-#endif // QGCUNCONNECTEDINFOWIDGET_H