Updating trunk VERSION from 4002.0 to 4003.0

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

Change-Id: I733f49fd407ca9cadb08665aecb1d393b977c483
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1978256Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#726691}

chrome/VERSION

 MAJOR=81
 MINOR=0
-BUILD=4002
+BUILD=4003
 PATCH=0