AudioDeviceBroker: restore use of hearing aids by default for VoIP calls

Remove the target SDK gating policy for the selection of hearing aids during
VoIP calls: this could break legacy apps that did not adopt new APIs to
manage hearing aids.

Bug: 295220577
Test: Meets, Skype, Zoom and Celluar calls with hearing aids.
Change-Id: I9e4abfe6d22ac48f50bdec362597a028359dcc9f