Improve callout shortcode. (#31802)

Remove the `markdownify` call, and instead rely on Hugo's proper syntax; `{{% callout %}}` when we want to the content to be processed as Markdown.

This allows for stuff like:

{{% callout info %}}
##### I'm an info callout!

```css
.foo {
  color: #fff;
}
```

{{< example >}}
<div class="alert alert-warning alert-dismissible fade show" role="alert">
  <strong>Holy guacamole!</strong> You should check in on some of those fields below.
  <button type="button" class="btn-close" data-dismiss="alert" aria-label="Close"></button>
</div>
{{< /example >}}
{{% /callout %}}

site/content/docs/5.0/utilities/text.md

@@ -21,9 +21,9 @@ Easily realign text to components with text alignment classes. For left, right,
 <p class="text-xl-left">Left aligned text on viewports sized XL (extra-large) or wider.</p>
 {{< /example >}}
 
-{{< callout info >}}
+{{% callout info %}}
 Note that we don't provide utility classes for justified text. While, aesthetically, justified text might look more appealing, it does make word-spacing more random and therefore harder to read.
-{{< /callout >}}
+{{% /callout %}}
 
 ## Text wrapping and overflow