If you want to completely disable the link of that photo, you should delete 29th and 31st line of your code (29th is the one with lightbox class, 31st is simply < /a>).
If you want photos to link somewhere else, it will need custom coding. You may want to change:
<?php echo wp_get_attachment_url( $myPhotoID ); ?>
placed in the 29th line of code to your desired value. Please keep in mind that I am working on unchanged version of that file, so lines of code might be different (if you changed anything in that file before).
Let me know if it helps you.