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.

PS2: Use constants for the strings, use proper key IDs.

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