Ensure `scrollable/highlights` container does not render in the main section

[cemms1]

What does this change?

Prevents Highlights container with scrollable/highlights type appearing in the main section of the front page.

Why?

This change was missed in https://github.com/guardian/dotcom-rendering/pull/12236 which ensures that when the Highlights container is swapped from fixed/highlights to scrollable/highlights that it is not rendered in the front main section