SPRINGFIELD — The chairman of a special committee investigating Democratic State House Speaker Michael J. Madigan’s role in a bribery scheme involving utility giant Commonwealth Edison has postponed the panel’s next meeting, which had been scheduled for Thursday.Rep. Emanuel Chris Welch, D-Hillside, announced Wednesday that the meeting is being delayed, in part because of the worsening COVID-19 pandemic and in part because it is still waiting to receive documents from ComEd.“The Committee is currently awaiting documents …