AudioCodingModuleImpl: Stop failing artificially for non-Opus encoders

All encoders already handle the "Opus-specific" requests sanely (by
failing nicely), so we don't need extra checks to protect them.

BUG=webrtc:5028

Review URL: https://codereview.webrtc.org/1527453005

Cr-Original-Commit-Position: refs/heads/master@{#11051}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 44307630d3ad6dcdd7b7fd07e78881b50a92ced4
5 files changed