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.
(cherry picked from commit 97014eff)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:6db4ead48e50356918e28594b13c31defdf009a1)
Merged-In: I9e4abfe6d22ac48f50bdec362597a028359dcc9f
Change-Id: I9e4abfe6d22ac48f50bdec362597a028359dcc9f