Debugger: Use override consistently

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

Change-Id: I6a20484716dc5bd84fe9592b40ae57be66fe32bf
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/memoryagent.h

@@ -74,7 +74,7 @@ class MemoryAgent : public QObject
 
 public:
     MemoryAgent(const MemoryViewSetupData &data, DebuggerEngine *engine);
-    ~MemoryAgent();
+    ~MemoryAgent() override;
 
     void updateContents();
     void addData(quint64 address, const QByteArray &data);