Update to "Default page": rename "In this section"

[koalie]

Further to #282

Describe the issue
When someone lands on a default page from the navigation menu, and this page lives in a different top-level directory, there may be confusion that the "In this section" list featured at the top right of a landing page does NOT match all the pages that are available at any given time via a navigation menu category.

URL
For example: https://www.w3.org/about/leadership/

Additional context
One may land on this page from the "About" navigation menu expecting that "In this section" will link to the other elements of the menu. But only 7 out of 12 entries are concerned as other entries all are in different directories of the site.

Recommended solution
Perhaps renaming "In this section" as "Related" would reduce confusion.