SPRINGFIELD — A 6-1 Illinois Supreme Court majority on Friday ruled that it can’t grant a post-conviction rehearing to a man after he’s already completed his sentence.The justices were asked to remand a case to the trial court for rehearing by a man who alleges he received ineffective assistance of counsel.The majority upheld the Illinois Post Conviction Hearing Act, which prohibits defendants, including Lanard Gayden, from filing direct appeals or post-conviction petitions after they have completed a …