SettingsProvider: don't set default value for advanced mode

The config value is not a default, but rather a 'always-on' switch.
Advanced mode should always be off by default on devices it shows up on
(aka retail user builds).

Ref: CYNGNOS-815

Change-Id: Ia017dd4bac726b445f2fc2b43bfbd0d2833eee0e
Signed-off-by: Roman Birg <roman@cyngn.com>