ScxmlEditor: Remove duplicated icons

Some of the icons that came with the scxml editor were already present
elsewhere in Qt Creator in a themable/HighDPI-able form.

Remove the own .png files, use the existing icons.

Change-Id: I891305faee45eeb39dac4135d2ff96fc06727731
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/scxmleditor/common/structure.cpp

@@ -42,6 +42,7 @@
 #include <QRegExpValidator>
 #include <QUndoStack>
 
+#include <utils/utilsicons.h>
 #include <utils/qtcassert.h>
 
 using namespace ScxmlEditor::PluginInterface;
@@ -103,6 +104,8 @@ Structure::Structure(QWidget *parent)
 {
     m_ui.setupUi(this);
 
+    m_ui.m_checkboxButton->setIcon(Utils::Icons::FILTER.icon());
+
     addCheckbox(tr("Common states"), State);
     addCheckbox(tr("Metadata"), Metadata);
     addCheckbox(tr("Other tags"), OnEntry);