fix(brightness suw): Hide brightness preference in the suw.

Root cause: there's a mismatch in how visibility is determined for
the AutoBrightnessPreferenceControllerForSetupWizard. The
getAvailabilityStatus method and the displayPreference method
(specifically the preference.setVisible call) use different
conditions for showing the preference.
Solution: To ensure consistency, I propose aligning these conditions
by incorporating an aconfig flag check in both places. This will
prevent unexpected behavior and make the logic clearer.

Bug: 389011125
Flag: com.android.settings.accessibility.add_brightness_settings_in_suw
Test: atest AutoBrightnessPreferenceControllerForSetupWizardTest
            BrightnessLevelPreferenceControllerForSetupWizardTest
Change-Id: I004bfe8b1e039734356715c971f0bfbe56ffa9db