Fix faulty Ci::Build#cache spec

spec/models/ci/build_spec.rb

@@ -270,7 +270,7 @@ describe Ci::Build do
           allow_any_instance_of(Project).to receive(:jobs_cache_index).and_return(1)
         end
 
-        it { is_expected.to include(key: "key:1") }
+        it { is_expected.to be_an(Array).and all(include(key: "key:1")) }
       end
 
       context 'when project does not have jobs_cache_index' do