Updating trunk VERSION from 4255.0 to 4256.0

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

Change-Id: I6b6f9f86f92aaec6a6869f6901e24314d43a1870
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2393630Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#804593}

chrome/VERSION

 MAJOR=87
 MINOR=0
-BUILD=4255
+BUILD=4256
 PATCH=0