Fix compile error when both of dist_8x8 and pvq are enabled
Fix compile error when both of dist_8x8 and pvq are enabled

Remove mistakenly leftover code from commit
e30a47ca0ff42ca16561ff6ba2099a4233a5bc75.

Note that this change force-disables activity masking in PVQ until we can add some
bitstream signaling for it.

Change-Id: I5279f82e7977733ebc40f5aed844ecec1279992a

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