Updating trunk VERSION from 4290.0 to 4291.0

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

Change-Id: I554caf2bb0df03c8bfe2e58ab007c67a81e8bcc2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2465087Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#816046}

chrome/VERSION

 MAJOR=88
 MINOR=0
-BUILD=4290
+BUILD=4291
 PATCH=0