Updating trunk VERSION from 4003.0 to 4004.0

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

Change-Id: I12ed7ebb633a983bcf40d0fd139ed3c94eaa5d4a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1978220Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#727028}

chrome/VERSION

 MAJOR=81
 MINOR=0
-BUILD=4003
+BUILD=4004
 PATCH=0