In the content.php file of the theme, you can find the following code at around line 51 and change it.
From:
<a class="wp-contenttitle" href="<?php the_permalink(); ?>" title="<?php the_title_attribute( array('before' => 'Permalink to: ', 'after' => '')); ?>"><?php the_title(); ?></a>
To:
<?php the_title(); ?>
This will remove the link from all titles, including in lists of blog posts, which means that clicking to title to continue to the full post will no longer work.