Fix comment in changelog template
This template is used to render the set of changes in the changelog page.
If this version of the spec is unstable, it expects to find a
- "changelog/newsfragments" directory containing all unreleased changes,
+ "changelogs/<api>/newsfragments" directory containing all unreleased changes,
and renders them all.
Otherwise it expects to find a "changelog/releases" directory, under which
