Remove card decks in favor of the grid

scss/_card.scss

@@ -150,30 +150,6 @@
 }
 
 
-// Card deck
-
-.card-deck {
-  .card {
-    margin-bottom: $card-deck-margin;
-  }
-
-  @include media-breakpoint-up(sm) {
-    display: flex;
-    flex-flow: row wrap;
-    margin-right: -$card-deck-margin;
-    margin-left: -$card-deck-margin;
-
-    .card {
-      // Flexbugs #4: https://github.com/philipwalton/flexbugs#flexbug-4
-      flex: 1 0 0%;
-      margin-right: $card-deck-margin;
-      margin-bottom: 0; // Override the default
-      margin-left: $card-deck-margin;
-    }
-  }
-}
-
-
 //
 // Card groups
 //

scss/_variables.scss

@@ -929,7 +929,6 @@ $card-bg:                           $white !default;
 $card-img-overlay-padding:          1.25rem !default;
 
 $card-group-margin:                 $grid-gutter-width / 2 !default;
-$card-deck-margin:                  $card-group-margin !default;
 
 
 // Tooltips

site/content/docs/4.3/migration.md

@@ -121,6 +121,7 @@ Badges were overhauled to better differentiate themselves from buttons and to be
 ### Cards
 
 - Removed the card columns in favor of a Masonry grid [See #28922](https://github.com/twbs/bootstrap/pull/28922).
+- Removed card decks in favor of the grid which adds more flexibility over responsive behaviour.
 
 ### Jumbotron