Improve efficiency of ArticlesCourses.update_from_course
Improve efficiency of ArticlesCourses.update_from_course

No need to load all the revisions when we only need distinct Article ids.

WikiEducationFoundation/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard