Debugger: Use override consistently

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

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

src/plugins/debugger/debuggeritemmanager.h

@@ -45,7 +45,7 @@ class DEBUGGER_EXPORT DebuggerItemManager : public QObject
 
 public:
     DebuggerItemManager();
-    ~DebuggerItemManager();
+    ~DebuggerItemManager() override;
 
     static QList<DebuggerItem> debuggers();