Remove zero shift
Remove zero shift

The shift dates back to experiment cb4x4. Now it's zero, should be
removed.

Change-Id: I1405b85c4044b8134f56035a20c5dfb0d154993e

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom