buffet: Remove unused URL

This variable was apparently never usd.

BUG=None
TEST=unittests

Change-Id: I06a79317a82946280d93c354db12df6bd2dedde3
Reviewed-on: https://chromium-review.googlesource.com/247503
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>