Fix DISALLOW_AMBIENT_DISPLAY blocks access to all lock screen display settings

"Ambient display" was merged into "Lock screen display", and the entry
was also moved from security page to display page and leveraged the
original user restriction of "Ambient display".

The user restriction should just work on the switch of Ambient display
instead of the "Lock screen display" entry.

Bug: 138177691
Test: robotest, visual
Change-Id: I5db0eb68c3aa6f4f7d8ecd42db2cdc72255b12f7