Updating trunk VERSION from 3967.0 to 3968.0

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

Change-Id: I15bf0d7a72238fda1ccdefb8d189e4dd71ebe435
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1915020Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#715177}

chrome/VERSION

 MAJOR=80
 MINOR=0
-BUILD=3967
+BUILD=3968
 PATCH=0