Updating trunk VERSION from 4028.0 to 4029.0

# This is an automated release commit.
# Do not revert without consulting chrome-pmo@google.com.
NOAUTOREVERT=true
TBR=govind@chromium.org

Change-Id: I74aeffaeb62dfaf0fc9d57f5349e3f4f7700492b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2001022Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#731819}

chrome/VERSION

 MAJOR=81
 MINOR=0
-BUILD=4028
+BUILD=4029
 PATCH=0