Update polaris.shopify.com/content/components/legacy-card.md

Co-authored-by: aveline <aveline@users.noreply.github.com>

Author: laurkim

polaris.shopify.com/content/components/legacy-card.md

@@ -1,6 +1,6 @@
 ---
 title: LegacyCard
-description: Cards are used to group similar concepts and tasks together to make Shopify easier for merchants to scan, read, and get things done.
+description: This is the legacy version of the Card component which is in the process of being updated to a new and more flexible and composable API. Cards are used to group similar concepts and tasks together to make Shopify easier for merchants to scan, read, and get things done.
 category: Structure
 keywords:
   - layout