Small correction singleton interface

GUI/mainwindow/ISingleton.h

@@ -26,15 +26,14 @@ public:
         return m_instance;
     }
 
-protected:
-    ISingleton() = default;
-    ~ISingleton() = default;
-
-private:
     ISingleton(const ISingleton&) = delete;
     ISingleton& operator=(const ISingleton&) = delete;
     ISingleton(ISingleton&&) = delete;
     ISingleton& operator=(ISingleton&&) = delete;
+    
+protected:
+    ISingleton() = default;
+    ~ISingleton() = default;
 };
 
 #endif // BORNAGAIN_GUI_MAINWINDOW_ISINGLETON_H