Remove BatteryFixSlice as it's not used

The BatteryFixSlice hasn't been used for a while, and it's introducing
memory leaks due to a design change at the framework's end. Hence,
remove it.

Bug: 245385410
Test: robotests
Change-Id: I517cab71a32613d5cb5fcd3beb991a24926a2902
Merged-In: I517cab71a32613d5cb5fcd3beb991a24926a2902
(cherry picked from commit e3fcf1f0)