Update sidekiq deferring-jobs doc to include Db health check based deferral
Context: gitlab-org/gitlab#404898 (comment 1417758008)
Update the docs to include the impact of gitlab-org/gitlab#404898 (closed) changes.
Context: gitlab-org/gitlab#404898 (comment 1417758008)
Update the docs to include the impact of gitlab-org/gitlab#404898 (closed) changes.