Redone work items don't update previous work item property

[anehx]

If a work item with the status redo is being reopened by the workflow, the property previous_work_item is not properly updated which results in a wrong workflow tree.

We should update the previous_work_item on the reopened work item when we reopen it here: https://github.com/projectcaluma/caluma/blob/71be79276b58d7292be2da444c3ad7174d21d7f8/caluma/caluma_workflow/utils.py#L117-L125