Remove BatteryStats ref from BackupRecord

BackupRecord currently maintains a record of
BatteryStatsImpl.Uid.Pkg.Serv, but never uses it, so the reference may
as well be removed.

Bug: 111763012
Test: Still compiles
Change-Id: I9c850a4aebf43a85b94a545fe6dbbfa7686c5ae0
2 files changed