Remove the test_version_has_unique_created_at unit test, which is no longer needed because of commit d7c0da03.
Remove the test_version_has_unique_created_at unit test, which is no longer needed because of commit d7c0da03.

technoweenie/acts_as_versioned,amberx/acts_as_versioned,asee/acts_as_versioned,ilabsolutions/acts_as_versioned,mjsommer/acts_as_versioned