CrOS: Update Chromite pin for release-R43.
CrOS: Update Chromite pin for release-R43.

Update pin for release-R43-6946.B to:
504196e05c2d8cb5448646a5f036431ec2ee5da1

TBR=stip@chromium.org
BUG=chromium:474713
TEST=None

Review URL: https://codereview.chromium.org/1084403005

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@294865 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build