Keep AVRCP vol sync on hearing protection trigger

This fix ensures that the AVRCP index is always fetched from the
VolumeStreamState using getVssForStreamOrDefault(), regardless of the
SoundDoseHelper check. By doing so, we always use the correct internally
stored volume index for AVRCP updates instead of the transient UI slider
value.

This maintains proper synchronization between internal audio volume
state and what is communicated over AVRCP, ensuring both safety and
consistency for Bluetooth devices under hearing protection enforcement.

Bug: 433986502
Test: manual
Flag: EXEMPT bugfix
Change-Id: I3d537d0dc5108356f74e9a42185612d9ed91f082