Do no convert FaceSettingsAttention to slice.

The check logic of this preference requires a page loading prior to
slice auto convertion, so it is not suitable to become a slice.
Converting it to a slice will lead to an app crash.

Fixes: 145723632
Test: robotests
Change-Id: Ie6eafb244e9a1cc9267f6b747c8e357d239e688e