ClassView: Replace QSharedPointer with std::shared_ptr

According to https://wiki.qt.io/Things_To_Look_Out_For_In_Reviews
QSharedPointer impl is poor and it's going to be removed from Qt 7.

Change-Id: I46a556c6ab558b4b86c7f9d767cac5b16302f326
Reviewed-by: hjk <hjk@qt.io>

src/plugins/classview/classviewmanager.h

@@ -4,7 +4,6 @@
 #pragma once
 
 #include <QObject>
-#include <QSharedPointer>
 #include <QStandardItem>
 
 namespace Utils { class FilePath; }
@@ -32,7 +31,7 @@ public:
     void onWidgetVisibilityIsChanged(bool visibility);
 
 signals:
-    void treeDataUpdate(QSharedPointer<QStandardItem> result);
+    void treeDataUpdate(std::shared_ptr<QStandardItem> result);
 
 private:
     void initialize();