config: Remove property vendor.fm.a2dp.conc.disabled

FM Playback Audio routes to A2DP path when BT Headset is connected.

The property vendor.fm.a2dp.conc.disabled is not used in FM
app as it is using app loopback for speaker and WHS(with BT connected)

FM app takes care of BT concurrency of not enabling FM over A2DP ,
Hence removing FM and a2dp concurrency changes from audio
modules.

CRs-Fixed: 2272694
Change-Id: I551ca9b0a9e060e72a6523ce7677234f2da2874f