fixup! fix(material/theming): restrict css color usage behind a flag

Author: wagnermaciel

src/material/core/style/_sass-utils.scss

@@ -68,7 +68,8 @@ $use-system-typography-variables: false;
     @return color.change($color, $args...);
   }
   @else if ($color != null and map.get($args, alpha) != null and $use-system-color-variables) {
-    @return rgb(from $color #{r g b} / map.get($args, alpha));
+    $opacity: map.get($args, alpha);
+    @return #{color-mix(in srgb, #{$color} #{($opacity * 100) + '%'}, transparent)};
   }
   @return $color;
 }

src/material/core/tokens/_m3-tokens.scss

@@ -170,7 +170,7 @@
     }
     @else if($color != null) {
       $result: map.remove($result, $opacity-key);
-      $combined-color: rgb(from $color #{r g b} / $opacity);
+      $combined-color: #{color-mix(in srgb, #{$color} #{($opacity * 100) + '%'}, transparent)};
       $result: map.set($result, $color-key, $combined-color);
     }
   }