In the content-featured.php, remove the following lines (from 5th line)
<?php if ( has_post_thumbnail() ): ?> <?php the_post_thumbnail('thumb-large'); // only difference to content.php ?> <?php elseif ( ot_get_option('placeholder') != 'off' ): ?> <img src="<?php echo get_template_directory_uri(); ?>/img/thumb-medium.png" alt="<?php the_title(); ?>" /> <?php endif; ?>
This will remove the big fat featured image in homepage of list of posts in hueman WordPress theme.