Make AudioEncoderFactory::Create pure virtual.
To finalize migrating AudioEncoderFactory to new interface for creating AudioEncoder and thus guarantee AudioEncoders always have an Environment at construction.
Bug: webrtc:343086059
Change-Id: I1d607082437c15201c8a75dd7a3925fe0f75b70f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/355800
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Jakob Ivarsson <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#42686}
e2f02c2df0