Apply correct styling for `<pre>` elements

Beforehand, \`<pre>\` elements would inherit the [`word-wrap`](https://developer.mozilla.org/en-US/docs/Web/CSS/word-wrap) property of
the `.from-content-api` CSS class, which is set to `break-word`.

We don’t want this behaviour for `<pre>` elements. Words should not be wrapped,
and instead the user can scroll horizontally to view the full line. This mirrors
the behaviour in R2 frontend.