Remove experimental twilight-based automatic brightness

Bug: 31602449
Test: verified adaptive brightness no longer varies with twilight with
"brightness_use_twilight" set to "1".

Merged-In: I6b5f7310020b2128c2b292414a205b6052270a0a
Change-Id: Ife9bf6d0f76df791cb7e6a22505d9f551da19731