Don't try to use CN if voice codec isn't mono
Don't try to use CN if voice codec isn't mono

Bug: chromium:878066
Change-Id: Iac6da4780a6da4fcfe2693d5cf826249a99f84c4
Reviewed-on: https://webrtc-review.googlesource.com/c/104601
Reviewed-by: Henrik Lundin <b9599afb29b1fa4305dba8bb04f760bf0c9c9471@webrtc.org>
Reviewed-by: Fredrik Solenberg <a86c06127c44de4932e34935a0755af178aabab6@webrtc.org>
Commit-Queue: Karl Wiberg <2c708eb0a58047bf403399f50b3da33ffd2dd444@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#25066}
ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc