You can remove them from the licenses folder on the system that the Management Console for Unix is installed on. You will have to open up each one to find the expired ones and then just delete them.
On Windows XP/2003 Server:
%SystemDrive%\Documents and Settings\All Users\Application Data\Quest Software\Management Console for Unix\licenses
On Windows 2008 Server/Vista/7/2012:
%SystemDrive%\ProgramData\Quest Software\Management Console for Unix\licenses
On Unix and Mac: /var/opt/quest/mcu/licenses