The Workflow Cleaning tab is available on the Troubleshooting and Support screen.
The Remove Approval Condition button, displayed on the tab, allows to remove the Approval conditions from all transitions of each workflow.
If all workflows have been successful cleaned a message informing is returned.
If any workflow has not been successful cleaned a message reports the list of workflows still affected by Approval Conditions.
It is expected that on uninstalling the add-on the Approval Conditions are automatically removed and this operation is suggested for troubleshooting exclusively.
If you have removed the condition from the workflows erroneously, you can restore it by running a re-indexing.