In ag/2642771, wakeup alarms is changed to based on screen-off
timebase. After that, all the wakeup alarms will be background
ones.
So it is safe to turn on the wakeupAlarm anomaly detector.
Bug: 65597330
Test: RunSettingsRoboTests
Change-Id: I653d4bbfa671c52890dc6c6b13870c666ba9b944