[7569] - See http://tracker.modx.com/issues/7569
Add a border bottom to collapsed panels

(cherry picked from commit 57f752a39ecc926dc6d46cc54cf1baaffb616d52)
Add changelog entry
[#7569] Add bottom border to collapsed panels

Merge branch 'bug-7569' into release-2.2

* bug-7569:
  Add changelog entry
  [7569] - See http://tracker.modx.com/issues/7569 Add a border bottom to collapsed panels