To delete a workflow state, go to Settings > Workspace Features > Workflows, find the workflow state you’d like to delete, and click on the state’s name.
In the menu that opens, click on the garbage can icon below the description field. You’ll be asked to confirm that you want to delete the workflow state; if so, click OK.
The workflow state will disappear from the state list, and you’ll see a success message pop up in the lower right confirming that the workflow state was deleted.
If you find you still have archived Stories in the workflow state, you can follow these instructions to access and delete archived Stories: Viewing/Editing Archived Stories.