Remove extra condition when handling absolute volume

Since now the AudioService is handling the SCO volume the same as any
other absolute volume device, there is no need of separate attenuation
adjustment on the APM side

Test: atest audiopolicy_tests
Bug: 393657380
Flag: android.media.audio.unify_absolute_volume_management
Change-Id: I1dd4902a32f6c77c30e017d815c108814b03b1fc