basically you'll have to remount the /system filesystem read-write, make the /system/media/audio/ui/camera_click.ogg unavailable (by either deleting it, renaming it, or changing its permissions), and eventually remount the /system filesystem read-only.
here is a script that you can put on your sdcard, and execute after each system upgrade (the name of your device's partition may be different):
mount -o remount,rw /dev/block/mtdbblock3 /system chmod 640 /system/media/audio/ui/camera_click.ogg mount -o remount,ro /dev/block/mtdbblock3 /system