The city of Chicago cannot be held liable for the way 45th Ward Alderman James Gardiner manages his official Facebook page, a federal judge held.In a written opinion, U.S. District Judge Sharon Johnson Coleman of the Northern District of Illinois dismissed the city as a defendant in a proposed class-action lawsuit accusing Gardiner of violating the First Amendment by purportedly suppressing dissent on his Facebook page.Coleman held the six constituents who filed the suit do not have standing under Article III of the U.S …