Redesign extended information page (#4322)

* Redesign extended information page

* Remove unused keys

* Add $ui-base-lighter-color variable to SCSS

app/javascript/styles/forms.scss

@@ -32,7 +32,7 @@ code {
       line-height: 18px;
       margin-top: 15px;
       margin-bottom: 0;
-      color: lighten($ui-base-color, 26%);
+      color: $ui-base-lighter-color;
 
       a {
         color: $ui-primary-color;
@@ -308,7 +308,7 @@ code {
       padding: 7px 4px;
       padding-bottom: 9px;
       font-size: 16px;
-      color: lighten($ui-base-color, 26%);
+      color: $ui-base-lighter-color;
       font-family: inherit;
       pointer-events: none;
       cursor: default;