OmniPreferenceTheme: use same track_on_color for light and dark

we made the settingslib do it the same in
8c6867551ab38f45c161584a6d68d3ccf3918fbf

also cleanup uneeded things that only makes it more
complicated and confusing

Change-Id: Ic36e52ebf2f2ffef4c35091a0feb9de40045cbc8
4 files changed