Merge pull request #8728 from amatsuda/model_all_returns_a_relation

A small fix for an AR test case

activerecord/test/cases/explain_test.rb

@@ -122,7 +122,7 @@ def test_silence_auto_explain
       base.expects(:collecting_sqls_for_explain).never
       base.logger.expects(:warn).never
       base.silence_auto_explain do
-        with_threshold(0) { Car.all }
+        with_threshold(0) { Car.all.to_a }
       end
     end