SPRINGFIELD – House Speaker Michael Madigan said Friday that he will not testify before the House Special Investigating Committee that is probing his role in a bribery scheme involving utility giant Commonwealth Edison, and it’s not likely that most of the other potential witnesses that Republicans want to hear from will testify either.In a two-and-a-half-page letter to the committee, Madigan called the committee “a political stunt” being orchestrated by House Republican Leader Jim Durkin, of Western Springs, and said the …