Fix non-virtual destructor

Author: nyalldawson

python/core/layout/qgslayoutundocommand.sip

@@ -112,7 +112,7 @@ class QgsLayoutUndoObjectInterface
 %End
   public:
 
-    ~QgsLayoutUndoObjectInterface();
+    virtual ~QgsLayoutUndoObjectInterface();
 %Docstring
  Destructor for QgsLayoutUndoObjectInterface.
 %End

src/core/layout/qgslayoutundocommand.h

@@ -132,7 +132,7 @@ class CORE_EXPORT QgsLayoutUndoObjectInterface
     /**
      * Destructor for QgsLayoutUndoObjectInterface.
      */
-    ~QgsLayoutUndoObjectInterface() = default;
+    virtual ~QgsLayoutUndoObjectInterface() = default;
 
     /**
      * Creates a new layout undo command with the specified \a text and \a parent.