Remove BTA_AV_SINK_INCLUDE

Remove the need to define BTA_AV_SINK_INCLUDE in addition to enabling
the profile_supported_a2dp_sink.  The code is already dependent on the
existance of sdp_a2dp_snk_handle, and the initialization of the
UUID_SERVCLASS_AUDIO_SINK which is only performed on devices including
A2DP Sink support.

Bug: 153203307
Test: atest BluetoothInstrumentationTests
Tag: #refactor
Change-Id: Ib259fd0b69d853ef21cb1852cd54237602a01f61