1) Please install and activate child theme, otherwise you will lose the changes when you upgrade the theme.Follow the link.
https://showthemes.zendesk.com/hc/en-us/articles/115002140769–Conference-Pro-Theme-How-to-activate-Conferencepro-child-theme-
2) Please copy conferencepro/components/templates/shortcodes/efcb_fullschedule.php to conferencepro-child/components/templates/shortcodes
3) Please create the folder structure in child theme.
4) Open conferencepro-child/components/templates/shortcodes/efcb_fullschedule.php
5) Around line number 91, you can find:
<div <?php echo $thumb_style; ?>>
</div>
6) Please change this to:
<div> <?php echo $title; ?>
</div>
7) Save the file.