You will have to edit the following template file in order to remove the second date,
/wp-content/plugins/another-events-calendar/public/partials/user/aec-public-edit-event-display.php
Note: Our current version doesn't have option to safely override our template files. So, the changes you made will be wiped out when you upgrade to our later versions. So, please remember to have a backup of this file before you upgrade to our latest versions. We will have option to override our layout files safely very soon.