fix link underline color (#15265)

packages/theme-chalk/src/link.scss

@@ -70,6 +70,11 @@ $typeMap: (
       @include when(disabled) {
         color: mix($primaryColor, $--color-white, 50%)
       }
+      @include when(underline) {
+        &:hover:after {
+          border-color: $primaryColor
+        }
+      }
     }
   }