Add `duration` attributes to Jobs API docs
Add `duration` attributes to Jobs API docs

Follow up to !13644.

mmkassem/gitlabhq,iiet/iiet-git,dreampet/gitlab,iiet/iiet-git,stoplightio/gitlabhq,axilleas/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,iiet/iiet-git,dreampet/gitlab,mmkassem/gitlabhq,axilleas/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,dreampet/gitlab