Revert "Allow SUW to change dark theme"

This reverts commit e07d6f7a.

Reason for revert:  155964222 The restored dark mode setting is applied before setupwizard finished, that make IME show as dark mode during setup
Bug: 155964222
Change-Id: Ic5152a8779cc855694a08ee566e45f99742e1b03

Change-Id: I81ecbd35ce141f4bc2b839993894829e61a9a279