CppTools: Use override consistently

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

Change-Id: I0e6d6a9df3e87b8042ccc5ea0adc70070a3821d6
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/plugins/cpptools/abstracteditorsupport.h

@@ -38,7 +38,7 @@ class CPPTOOLS_EXPORT AbstractEditorSupport : public QObject
     Q_OBJECT
 public:
     explicit AbstractEditorSupport(CppModelManager *modelmanager, QObject *parent = 0);
-    ~AbstractEditorSupport();
+    ~AbstractEditorSupport() override;
 
     /// \returns the contents, encoded as UTF-8
     virtual QByteArray contents() const = 0;