vp9-rtc: Reduce thresholds for skip golden
vp9-rtc: Reduce thresholds for skip golden

For nonrd-pickmode CBR mode: reduce the skip
golden ref thresholds, to reduce some psnr
regression in some clips, while still effectively
reducing flashing block artifact occurrence.

Change-Id: I468dcf5354411aeb54ac3ef56c6fb73267d93fde

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