Core: Use override consistently

clang-tidy fixes from modernize-use-override check.

Change-Id: If33399d60e96cae766bbedbe30044ada411e862f
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/actionmanager/commandmappings.h

@@ -46,7 +46,7 @@ class CORE_EXPORT CommandMappings : public QWidget
 
 public:
     CommandMappings(QWidget *parent = 0);
-    ~CommandMappings();
+    ~CommandMappings() override;
 
 signals:
     void currentCommandChanged(QTreeWidgetItem *current);