Don't save default doze brightness

The default doze brightness shouldn't replace the user's chosen manual brightness.

Bug: 372465405
Flag: EXEMPT bugfix
Test: atest DisplayPowerControllerTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:8d1d95cdc648d3f4ba54893983b3d571502d198d)
Merged-In: I8f0032ce473c0aad89bb621498ce2daeb3cfcc14
Change-Id: I8f0032ce473c0aad89bb621498ce2daeb3cfcc14
2 files changed