chore(samples): revert card sample styles

Author: didimmova

src/app/layouts/card/card-styling-sample/card-styling-sample.component.scss

@@ -41,7 +41,7 @@ igx-divider {
 //     $outline-color: #f0f0f0,
 //     $resting-shadow: none,
 //     $hover-shadow: none,
-//     $header-text-color: red,
+//     $header-text-color: #000000e0,
 // );
 
 // $custom-avatar-theme: avatar-theme(