Updating trunk VERSION from 4187.0 to 4188.0

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

Change-Id: Idb71c527a8c538ba12c4c68f87fddb31da717912
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2274819Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#783806}

chrome/VERSION

 MAJOR=86
 MINOR=0
-BUILD=4187
+BUILD=4188
 PATCH=0