AOSP/DeskClock - update the DeskClock version to target P (28) or higher.

Bug: 115499280

Test: manual - Ran the following CTS tests on Pixel phone. Tested the DeskClock UI.

$ make -j 40
  -rw-r--r-- 1 rtenneti primarygroup 5268958 Dec 11 16:54 ./out/target/product/marlin/system/app/DeskClock/DeskClock.apk

$ adb install -r out/target/product/marlin/system/app/DeskClock/DeskClock.apk

Change-Id: Ie4e53c003716591ce020a747928e99064194374b