Updating trunk VERSION from 4280.0 to 4281.0 and incrementing major version to 88

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

Change-Id: I9b20a18690f4cf3c7b0b58cdf88ba798e4800d3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2444534Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#813063}

chrome/MAJOR_BRANCH_DATE

-MAJOR_BRANCH_DATE=2020-08-21
+MAJOR_BRANCH_DATE=2020-10-02

chrome/VERSION

-MAJOR=87
+MAJOR=88
 MINOR=0
-BUILD=4280
+BUILD=4281
 PATCH=0