Ewoks inputs/outputs that are hidden from Orange show up in `get_task_inputs`/`get_task_outputs` method of the Orange widget

This raises issues when trying for example to propagate outputs downstream:

• the input/output is listed by get_task_outputs: https://gitlab.esrf.fr/workflow/ewoks/ewoksorange/-/blob/529b57b83ebdd0a8905630032dcb2d06f1d4c532/src/ewoksorange/bindings/owwidgets.py#L378
• but since it is not in Orange, _get_output_signal fails: https://gitlab.esrf.fr/workflow/ewoks/ewoksorange/-/blob/529b57b83ebdd0a8905630032dcb2d06f1d4c532/src/ewoksorange/bindings/owwidgets.py#L357