TextEditor: Remove RefactoringChanges::m_data

There is no use for a data member in the base class.

Change-Id: I126d8713d2a7bf4061ecbd60b4c144d39c08d550
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/cppeditor/cpprefactoringchanges.h

@@ -98,7 +98,7 @@ public:
     const CPlusPlus::Snapshot &snapshot() const;
 
 private:
-    CppRefactoringChangesData *data() const;
+    const QSharedPointer<CppRefactoringChangesData> m_data;
 };
 
 } // namespace CppEditor