Make Gerrit the default for libyuv code reviews

BUG=665585

Change-Id: I96e92b1d22051c60808f4563e0f3c70f5a801efd
Reviewed-on: https://chromium-review.googlesource.com/430222Reviewed-by: Frank Barchard <fbarchard@google.com>
Commit-Queue: Aaron Gable <agable@chromium.org>

codereview.settings

 # This file is used by git cl to get repository specific information.
 CODE_REVIEW_SERVER: codereview.chromium.org
+GERRIT_HOST: True
 PROJECT: libyuv
 TRY_ON_UPLOAD: False
 VIEW_VC: https://chromium.googlesource.com/libyuv/libyuv/+/