Given that you have two identical methods (signatures, body, input/output) that you wanted to refactor into just one, what type of Work Item from the MS Agile template would be most appropriate? Task, Bug, Quality of Service, Risk? Why?
I would create a user story called "Refactoring duplicate methods" and plan it in an iteration. Then besides only removing this duplicate, also take some time to check on other duplicate items.
If you are sure it is only this only task, then you could have a standing user story and bind a task to it. It is a good practice to have all work attached to a bug or user story.