Removes "reset" button from shortcuts screen.

As per UX, full-screen pickers for individual parts of customization
should not contain their own "reset" button. Instead, the "reset" button
should only be available on the main screen.

This CL removes that button from the keyguard quick affordance (lock
screen shortcuts) screen.

Bug: 266116562
Test: manually verified that the "reset" button is gone from the
shortcuts screen but it still showing as expected on the main screen.

Change-Id: Iebdc6da5cb8c71af8404045332b0a6d05caa2767