Revert "Optimize RDMULT values for key frames"

Revert "Optimize RDMULT values for key frames"

This reverts commit b13f6154df9c0834d74f7e3d41e41c4208f56d18.

Temporarily revert this change due to interactions with rate control at very low target bit-rate.

Original change's description:
> Optimize RDMULT values for key frames
>
> Encoding of 5 frames of each sequence using key frames only, the new
> values help the metrics by:
>
>          PSNR     SSIM       PSNR-HVS
> lowres:  -0.870%  -0.140%    -0.892%
> midres:  -0.899%  -0.146%    -1.052%
> hdres:   -0.944%  -0.115%    -1.028%
>
> Tested q range:
> 2 6 10 14 18 22 26 30 34 38 42 46 50 54 58 62
>
> Change-Id: I5b0dda366d589f52987c5bad11a1f95c4e6dc1a5

TBR=yaowu@google.com,paulwilkins@google.com,jingning@google.com,builds@webmproject.org

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

Change-Id: Ie1e4cf21308d69699a65a393a83884882682ea8e