Change expected status code of job artifacts API response

See https://gitlab.com/gitlab-org/gitlab-ee/issues/3417

spec/requests/api/jobs_spec.rb

@@ -304,7 +304,7 @@ def get_artifact_file(artifact_path)
             let(:api_user) { nil }
             it 'does not return specific job artifacts' do
-              expect(response).to have_http_status(401)
+              expect(response).to have_http_status(404)
             end
           end
         end