Rename wxDataViewEvent::SetEditCanceled() and remove its argument

This method should be only used when the edit is really cancelled, so it
doesn't need to take a boolean argument.

It should also use the same spelling as IsEditCancelled() (and for
consistency with the rest of wxWidgets API which uses British English).

Also remove this method from the documentation, it is not part of the
public API.

interface/wx/dataview.h

@@ -3818,7 +3818,6 @@ public:
      */
     wxDataViewItem GetItem() const;
     void SetItem( const wxDataViewItem &item );
-    void SetEditCanceled(bool editCancelled);
     void SetPosition( int x, int y );
     void SetCache(int from, int to);
     wxDataObject *GetDataObject() const;