As you’ve probably already seen, the border is coming from line 107 –
blockquote,
input,
select,
textarea,
.author-box,
.breadcrumb,
.sticky,
.taxonomy-description,
.wp-caption {
background-color: #f6f6f6;
border: 1px solid #111111;
}
But if that’s the part you need to keep for other parts of your site, you could either remove the line that says .breadcrumb,
in the code above….or you could create it on a separate line and add border: none;