OmniTorch: Fix Bright setting not being removed when unsupported by a device.

These are in a PreferenceCategory, so they have to be removed via the category, as theoretically there could be another PreferenceCategory containing a preference with the same key.

The WidgetSettings key was renamed for consistency and because I couldn't get this fix work with the old key name.

PS1;
-cleanup

Change-Id: I14c06ac9228b31059f611aaaa4da4b8d23070a82
Signed-off-by: Kyle Repinski <repinski23@gmail.com>