Merge branch 'stable-2.9'

* stable-2.9:
  Documentation: Set page width to 900px centered
  Review UI docs: Remove 'Edit' action button from screenshots
  Add missing `=` in AccountConstants.properties
  Add unit test for copying label approvals during cherry-pick

Change-Id: Icabdbef3d9b5ff9650bfa4e6475e84a94c7ef41e