make Card size prop optional (#1359)

Author: jasonbasuil

src/Card/Card.stories.tsx

@@ -22,7 +22,6 @@ export function Default() {
       divided={false}
       helperText="(helper text)"
       noPadding={false}
-      size="sm"
       subTitle="Subtitle"
       title="Default card title"
     />

src/Card/Card.tsx

@@ -29,7 +29,7 @@ type CardProps = {
   loadingSkeleton?: ReactNode;
   loadingSkeletonParagraphCount?: number;
   noPadding?: boolean;
-  size: 'xs' | 'sm' | 'md' | 'lg';
+  size?: 'xs' | 'sm' | 'md' | 'lg';
   subTitle?: ReactNode;
   title?: ReactNode;
 } & ElementProps;