Remove throws RuntimeException from APIs

As API review feedback, the information provides no value to a
user. Remove it from BatteryStatsManager#reportWifiRadioPowerState
and BatteryStatsManager#reportMobileRadioPowerState.

Fix: 184735838
Test: make update-api
Change-Id: I8cce6523695ba58654cbe5d1db79045eeb46d913