Remove gesture shortcut restoration/merge logic from AMS

The gesture shortcut is restored in SettingsBackupAgent. In Setup
Wizard, there is no way for the user to turn on a gesture shortcut
because in Setup Wizard, it's in button navigation mode, hence no
gesture navigation available.

Bug: N/A
Test: N/A
Flag: EXEMPT comment only
Change-Id: I5fcd606ea645ae57b71420656ce0c30916471e65