Revert of Enable trendline experiment and bayesian bitrate estimator experiment by default. (patchset #6 id:100001 of https://codereview.webrtc.org/2777333003/ )

Reason for revert:
API changes in webrtc/sdk/objc/Framework/Headers/WebRTC/RTCFieldTrials.h broke internal project

Original issue's description:
> Enable trendline experiment and bayesian bitrate estimator experiment by default.
>
> BUG=webrtc:6566, webrtc:7415
>
> Review-Url: https://codereview.webrtc.org/2777333003
> Cr-Commit-Position: refs/heads/master@{#17491}
> Committed: https://chromium.googlesource.com/external/webrtc/+/27925de9512c67c9934ba535dc83ffe04ed999fe

TBR=terelius@webrtc.org,stefan@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6566, webrtc:7415

Review-Url: https://codereview.webrtc.org/2791743002
Cr-Original-Commit-Position: refs/heads/master@{#17495}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 029f7cccf44da11559cdb5e74bf83b42ee98b039
8 files changed