Use design capacity instead of full charge capacity

Full charge capacity is already included as part of
health HAL 1.0. Concluded in b/149121450 to add a value
that is valuable.

Bug: 149428646
Bug: 149121450
Test: lshal debug android.hardware.health@2.1::IHealth/default
Change-Id: Iadf3c14850df57034378dcc10cdbab0eb43c3aae