Merge pull request #15768 from zuhao/refactor_activesupport_concern_test

Move test teardown into `ensure` block.

activesupport/test/core_ext/kernel/concern_test.rb

@@ -6,7 +6,8 @@ def test_may_be_defined_at_toplevel
     mod = ::TOPLEVEL_BINDING.eval 'concern(:ToplevelConcern) { }'
     assert_equal mod, ::ToplevelConcern
     assert_kind_of ActiveSupport::Concern, ::ToplevelConcern
-    assert !Object.ancestors.include?(::ToplevelConcern), mod.ancestors.inspect
+    assert_not Object.ancestors.include?(::ToplevelConcern), mod.ancestors.inspect
+  ensure
     Object.send :remove_const, :ToplevelConcern
   end
 end