wx set editor doesn't rebuild on item deletion

When items are deleted from list of available values, the editor is supposed to update the underlying object *and* the editor. However, in this scenario wx set editor returns without updating the editor:
https://github.com/enthought/traitsui/blob/bdb11ada13421a4a9dbe63c0c3d7ebf8f5a53f98/traitsui/wx/set_editor.py#L212-L223

The solution to the issue is to simply remove this return statement.