This flag was used to protect an AdaptationListener from adapting again,
but since AdaptationListener was removed this guard is no longer needed.
Bug: webrtc:11834
Change-Id: If79e960f57aaf56ce2849329ff6737414fc60e9a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/181068
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@google.com>
Cr-Commit-Position: refs/heads/master@{#31905}