The Nominating Committee of the Alumni Council has placed in nomination two alumni for the position of alumni trustee, with three-year terms to begin at Commencement 1998.         Nominated for a second term is Audrey Hittinger Katz '57. Katz lives in Silver Spring, Md., and is vice president of Data-Prompt, Inc., a data processing company. Katz serves on the Student Affairs and Technology committees of the Board of Trustees and is a member of the Colby Friends of Art.     Nominated for a first, renewable term is Anne Ruggles Gere '66. Gere, who resides in Ann Arbor, Mich., and St. Louis, Mo., is a professor of English at the University of Michigan. She has been a Colby overseer since 1997. She also has been involved in a number of alumni activities and events. If elected, her term as alumni trustee would begin this summer and run through Commencement 2001.