Updating trunk VERSION from 4437.0 to 4438.0

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

Change-Id: Ia8945cebd41ea97ec5d30312d03e9f13f6b37377
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2739074
Bot-Commit: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#860116}

chrome/VERSION

@@ -1,4 +1,4 @@
 MAJOR=91
 MINOR=0
-BUILD=4437
+BUILD=4438
 PATCH=0