Clean up by removing unused field-trial that was added in this CL https://webrtc-review.googlesource.com/c/src/+/151911 to make it possible to simulate a slow decoder. Bug: None Change-Id: I237f3ac6baae76f81fcd2938e43eab9c19cea45f Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/261681 Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Johannes Kron <kron@webrtc.org> Cr-Commit-Position: refs/heads/main@{#36824}