Remove `num_op` from PostProcessingModule
We should remove num_op from PostProcessingModule as it is not used. See https://gitlab.com/teklia/atr/dan/-/blob/2adb6ba8e9f7698b3f7968292a87c6dde920f42b/dan/post_processing.py#L18
We should remove num_op from PostProcessingModule as it is not used. See https://gitlab.com/teklia/atr/dan/-/blob/2adb6ba8e9f7698b3f7968292a87c6dde920f42b/dan/post_processing.py#L18