Some code samples need updating for best practice

[MelSumner]

Reading through https://guides.emberjs.com/release/components/template-lifecycle-dom-and-modifiers/

There are some code samples that could use an update, as they are out-of-date for best practices.

Specifically, the examples showing an article element containing a header and an h1.

These days, it's really best to have one header and one h1 per page. It would be fine to change these to divs with demonstrative classes on them, e.g.,

<article>
  <div class="article__title">{{@title}}</div>
  <div class="article__content">{{@body}}</div>
</article