The Chicago Teachers Union is not violating the First Amendment by limiting its members to the month of August to revoke their authorization to have dues deducted from their paychecks, a federal judge held.In a written opinion last week, U.S. District Judge John Z. Lee threw out a proposed class-action lawsuit filed against the union and the Chicago Board of Education by Joanne Troesch and Ifeoma Nkemdi. Troesch is a technology coordinator at Jones College Prep in the South Loop and Nkemdi is a second-grade teacher at …