If you do not want to use the test pilot add-on you can uninstall it. For details of how to uninstall it see https://support.mozilla.com/kb/Uninstalling+add-ons - in the add-ons manager the test pilot add-on is called Feedback. You have not said what version of Firefox you are currently using so it is not clear what older version you want. The test pilot option is available in the development/Aurora versions, if you want the current release version, you can get Firefox 4.0.1 from http://www.mozilla.com/