Simplify changing "delete/remove" links styles

Since we're only changing the style of the border in one case and the
color in the other case, we don't have to duplicate the code for every
property.

This makes it easier for other CONSUL installations to customize these
borders.

app/assets/stylesheets/admin.scss

@@ -451,7 +451,7 @@ code {
   &:hover,
   &:active,
   &:focus {
-    border-bottom: 1px dotted #fff;
+    border-bottom-color: transparent;
     color: #cf2a0e;
   }
 }

app/assets/stylesheets/layout.scss

@@ -2497,7 +2497,7 @@ table {
   &:hover,
   &:active,
   &:focus {
-    border-bottom: 1px solid #cf2a0e;
+    border-bottom-style: solid;
     color: #cf2a0e;
     text-decoration: none;
   }