remove references to obsolete test files
remove references to obsolete test files

These files have been removed from test/test-data.mk. When they are not
found, new versions are encoded. However, if they happen to exist, the
tests fail due to the unsupported bitstreams.

Change-Id: Ib643a5a22608b20df2b8f520691ba213f07837e1

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