Adjust answer export test to include pinned_at field

spec/lib/use_case/data_export/answers_spec.rb

@@ -32,7 +32,8 @@ describe UseCase::DataExport::Answers, :data_export do
               user_id:       user.id,
               created_at:    "2022-12-10T13:37:42.000Z",
               updated_at:    "2022-12-10T13:37:42.000Z",
-              smile_count:   0
+              smile_count:   0,
+              pinned_at:     nil
             }
           ]
         }