Updating trunk VERSION from 4042.0 to 4043.0

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

Change-Id: I32c2947ce269b9bf83057cfe152b3794154b7147
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2026471Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#736225}

chrome/VERSION

 MAJOR=81
 MINOR=0
-BUILD=4042
+BUILD=4043
 PATCH=0