Minor changelog fix

This will be missing from the last release, but it will be fixed in
the changelog for `main` and future releases.

Author: sirosen

CHANGELOG.rst

@@ -13,7 +13,8 @@ Unreleased
 0.28.6
 ------
 
-- Update vendored schemas (2024-06-23)
+- Update vendored schemas: bitbucket-pipelines, circle-ci, readthedocs,
+  renovate (2024-06-23)
 - Add CircleCI schema and pre-commit hook. Thanks :user:`jrdnbradford`! (:pr:`444`)
 
 0.28.5