Only show the schedule text for the night display and dark theme

In Android S design, night display and dark theme only show
schedule text for summary.

- Rmove redundant string resource.
- Remove redundant method in night display formatter.
- Refactor the code in dark mode preference and night display
controller.

Test: See the correct behavior in screen.
Fix: 174964139
Change-Id: I658b3073a0a6ed83f589103999c711e5430eaeb7