change uniq to distinct for SQL queries to fix deprecation

app/controllers/admin/questions_controller.rb

@@ -11,7 +11,7 @@ module Admin
     end
 
     def show
-      @registrations = @conference.registrations.joins(:qanswers).uniq
+      @registrations = @conference.registrations.joins(:qanswers).distinct
     end
 
     def new

app/controllers/admin/versions_controller.rb

@@ -9,7 +9,7 @@ module Admin
       if current_user.has_role? :organization_admin, :any
         @conferences_with_role = Organization.with_role('organization_admin', current_user).map { |org| org.conferences.pluck :short_title }.flatten
       end
-      @conferences_with_role.uniq!
+      @conferences_with_role.distinct!
 
       return if @conference.blank?
       @versions = PaperTrail::Version.where(conference_id: @conference.id).accessible_by(current_ability)

app/controllers/admin/volunteers_controller.rb

@@ -14,7 +14,7 @@ module Admin
     def show
       if can_manage_volunteers?(@conference)
         @volunteers = if @conference.use_vpositions
-                        @conference.registrations.joins(:vchoices).uniq
+                        @conference.registrations.joins(:vchoices).distinct
                       else
                         @conference.registrations.where(volunteer: true)
                       end