Disable the ContentProtection setting switch bar when current user is a guest user.

Bug: 337774836
Test: m -j256 Settings && atest
SettingsRoboTests:ContentProtectionTogglePreferenceControllerTest
Flag: EXEMPT bugfix

(cherry picked from commit baf50305)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ef16a8cbef5e0987a37c2fa9e5091672a3c8e4ab)
Merged-In: I36173b2e7027765b526dfa2ebca216a7de71e669
Change-Id: I36173b2e7027765b526dfa2ebca216a7de71e669