Use Font Awesome icons on related content actions

We've deprecated the "icons" font since we started using Font Awesome
two years ago.

app/assets/stylesheets/layout.scss

@@ -2529,33 +2529,16 @@ table {
   a {
     font-weight: bold;
     margin-right: $line-height;
-    padding-left: rem-calc(20);
-    position: relative;
     text-decoration: none;
 
-    &.score-positive::before,
-    &.score-negative::before {
-      font-family: "icons";
-      left: 0;
-      position: absolute;
-    }
-
     &.score-positive {
+      @include has-fa-icon(check, solid);
       color: $color-success;
-
-      &::before {
-        color: $color-success;
-        content: "\6c";
-      }
     }
 
     &.score-negative {
+      @include has-fa-icon(times, solid);
       color: $color-alert;
-
-      &::before {
-        color: $color-alert;
-        content: "\76";
-      }
     }
   }
 }