Update performance test results for tune=SSIM
Update performance test results for tune=SSIM

I made a mistake (used the outdated baseline) in the CL I
submitted earlier this week:
https://chromium-review.googlesource.com/c/webm/libvpx/+/1638854

The corrected results are following:
The additional gains/loss on top of the tune=ssim are:
Data Set   Overall PSNR   SSIM       MS-SSIM
 Lowres       3.490      -3.164      -2.267
 Midres       2.245      -2.270      -2.287
 HDres        2.562      -1.804      -1.681
Lowres_10bd   3.477      -2.399      -2.689
Midres_10bd   3.467      -1.534      -1.636

The overall gains/loss comparing to tune=psnr are:
Data Set   Overall PSNR   SSIM       MS-SSIM
 Lowres       6.127      -5.818      -4.783
 Midres       4.574      -5.383      -6.242
 HDres        4.908      -6.218      -7.106
Lowres_10bd   6.115      -6.212      -7.790
Midres_10bd   6.238      -6.064      -7.249

Change-Id: Iae72482f7b30f200e5021a98c920eed841d0972a

webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx