Reset column info after making Topic tz-aware

In AttributeMethodsTest, we make the global Topic class time zone-aware
which changes instance date time attribute casting behaviour. We need to
reset column info after the test because future tests don't expect Topic
date time columns to be time zone-aware.

activerecord/test/cases/attribute_methods_test.rb

@@ -711,6 +711,10 @@ def topic.title() "b" end
       record.written_on = "Jan 01 00:00:00 2014"
       assert_equal record, YAML.load(YAML.dump(record))
     end
+  ensure
+    # NOTE: Reset column info because global topics
+    # don't have tz-aware attributes by default.
+    Topic.reset_column_information
   end
 
   test "setting a time zone-aware time in the current time zone" do