Golden files test is broken due to missing archive

[grafail]

The test corpus in the url is not there any more, thus the test cannot be run.

guetzli/tests/golden_test.sh

Line 14 in 214f2bb

curl https://storage.googleapis.com/test-image-corpus/test-corpus.tgz | tar -C $INPUT_DIR_PNG -zxf - || exit 2