Method 1: Basic iTunes Restore (No Data Loss)
Connect your phone to your computer and open iTunes. Select your device in the left menu and click on the “Restore” button.
iTunes will ask to backup your device — select yes. It will only backup non-jailbroken applications and will restore all of your app store applications and preferences.
The new firmware will be downloaded, extracted, and installed. Your device will restart when it is finished.
After your iPhone activates you can restore from your backup (if you created one) and you will get all of your non-jailbreak applications back. Your phone will still be un-jailbroken if you do this.
All set! Your phone should no be back to normal with little or no traces of jailbreaking activity