Revert "vp8: Increase rate threshold for overshoot-drop"

Revert "vp8: Increase rate threshold for overshoot-drop"

This reverts commit bc066684ca4deff24d02ee56071d731b431bf438.

Reason for revert: <INSERT REASONING HERE>
Regression in webrtc perf test

Original change's description:
> vp8: Increase rate threshold for overshoot-drop
>
> Increase the rate threshold for the dropping when
> overshoot is detected during encoding. This helps
> to prevent some unneccessary drops for hard content.
>
> Change-Id: I258bf33883d46347efd44e1e192cb25c444d05fe

TBR=sprang@chromium.org,marpan@google.com,builds@webmproject.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Ib0e84747430ba6d04e479f9efd86d628b80a1e67