Remove Rietveld CQ config.

Rietveld CQ has already been disabled and is no longer supoorted.

No-Try: True
Bug: chromium:770592
Change-Id: Idc3324bb9058eef1c5895f61e082c68bd98e5715
Reviewed-on: https://chromium-review.googlesource.com/714533


Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>