Docs: mention the use of .flex-row for .card-body usage (#42765)

Co-authored-by: Mark Otto <markd.otto@gmail.com>

Author: julien-deramond

site/src/content/docs/guides/migration.mdx

@@ -223,7 +223,7 @@ Bootstrap 6 is a major release with many breaking changes to modernize our codeb
   - Theme coloring via `.theme-*` classes on the `.accordion` wrapper.
 - **Rebuilt close button markup.** `.btn-close` now renders its icon via a CSS `mask-image` (`--btn-close-icon`) tinted with `background-color: currentcolor`, so the button is self-contained—no child `<svg>` is required. The filter-based dark mode approach (`$btn-close-white-filter`) has been replaced by `currentcolor` inheritance, and the `.btn-close-white` class has been removed—on dark backgrounds (e.g., `.text-bg-dark`) the icon now inherits the contrast color automatically.
 - **Removed `.alert-dismissible`.** Dismissible alerts no longer require the `.alert-dismissible` modifier class. Place a `.btn-close` directly inside the alert—the alert's flex layout positions it automatically. Remove any `.alert-dismissible` class from your markup.
-- **Restructured cards.** Borders now live on `.card-body` and `.card-list` segments rather than a single outer `.card` border. Added `--card-box-shadow` and `--card-body-gap` tokens. New variant classes: `.card-translucent` (frosted glass effect) and `.card-subtle` (themed with subtle backgrounds). Horizontal cards use a new `.card-row` class. Removed `.card-link` class.
+- **Restructured cards.** Borders now live on `.card-body` and `.card-list` segments rather than a single outer `.card` border. Added `--card-box-shadow` and `--card-body-gap` tokens. New variant classes: `.card-translucent` (frosted glass effect) and `.card-subtle` (themed with subtle backgrounds). Horizontal cards use a new `.card-row` class. Removed `.card-link` class. `.card-body` is now a flex column container. You may need to add `.flex-row` when using additional flex utilities for custom layouts.
 - **Card groups now use container queries.** `.card-group` switches to its attached, equal-width row layout with a `@container` query instead of a viewport `@media` query, so it responds to the width of a parent query container rather than the viewport. Wrap the card group in a query container—e.g. add the `.contains-inline` utility to a parent element—or the cards stay stacked.
 - **List group horizontal variants now use container queries.** The `.*:list-group-horizontal` classes switch between vertical and horizontal layouts with `@container` queries instead of viewport `@media` queries, responding to a parent query container rather than the viewport. Wrap the list group in a query container (e.g. `.contains-inline`) for the responsive variants to take effect.
 - **Reworked badge variants.** Badge color variants now use `.badge-subtle` and `.badge-outline` combined with `.theme-*` classes (e.g., `.badge-subtle .theme-primary`), replacing the v5 `.bg-primary` utility pattern on badges.