A public workers union did not violate the First Amendment by limiting a member to a 15-day period each year to withdraw her authorization for dues to be deducted from her paycheck, a federal appeals court held.The 7th U.S. Circuit Court of Appeals on Friday rejected the argument that Susan Bennett was forced to subsidize the union in violation of her rights to free speech and free association after she submitted her resignation.When Bennett began working as a custodian for the Moline-Coal Valley School District in August …