Revert "Add theme mode design let user can choose theme self"

The CL was intended only for P as a temporary solution.
This reverts commit f0800fa3bd6d5279df3a183cc35ca5489112d73e.

Test: switch wallpapers, observe theme
Bug: 110758454
Change-Id: If10e4d87b6ddac10063b2671abd99e0baccdf92e
3 files changed