either change the field type to text and echo it out as you currently are or remove the tag and echo out the link as is:
<button class="claim-button"><?php echo CFS()->get( 'tracking_url' ); ?></button>
http://customfieldsuite.com/field-types/hyperlink.html
OR (and this would be my choice if I was you) Switch to ACF and use that for all your custom fields. in which case you would probably do this:
<button class="claim-button"> <a href="https://wordpress.stackexchange.com/questions/254506/<?php echo get_field("tracking_url'); ?>">Claim Bonus</a> </button>