Fix failing spec: ee/spec/controllers/groups/settings/ci_cd_controller_spec.rb

CI/CD group settings can now only be modified by owners per
https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2750/diffs.

ee/spec/controllers/groups/settings/ci_cd_controller_spec.rb

@@ -7,7 +7,7 @@ describe Groups::Settings::CiCdController do
   let(:user) { create(:user) }
 
   before do
-    group.add_maintainer(user)
+    group.add_owner(user)
     sign_in(user)
   end