Delete unnecessary description.

src/client/styles/scss/_override-bootstrap-variables.scss

@@ -25,7 +25,6 @@ $gray-900: darken($dark, 5%) !default;
 $grays: ("50": $gray-50) !default;
 $red: #ff0a54 !default;
 
-$border-color: $gray-300 !default;
 
 //== Typography
 //