Press and hold the ‘Home/Hold For Commands’ button, select ‘Reset User Presets’ and press the ‘Save’ knob to reset the User bank to its factory presets.

This can also be done via the Line6 Monkey program. While in the Line6 Monkey program, when you get to the Patch Management Options screen, choose:
"Install the new default patches included in this update (all existing patches will be erased)."

Note: this will not change any model packs installed on your unit