Revert "Audio: Add Pause/Resume in AMR-WB tunnel recording"

This reverts commit e51f3b1dd8b8b2668af3c467a330b18714d29966.

There's no mSource->stop() in MPEG4Writer::Track::pause(),
so no need to add this limitation here.

CRs-Fixed: 620437

Change-Id: I7b7134e2f58083b7dd9cfb3c0943d703ba228ecb