Incrementing VERSION to 131.0.6778.39

Change-Id: I403e8dc9cde113033c0ef91027a98f7fc34be071
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5995146
Bot-Commit: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/6778@{#1752}
Cr-Branched-From: b21671ca-refs/heads/main@{#1368529}

chrome/VERSION

 MAJOR=131
 MINOR=0
 BUILD=6778
-PATCH=38
+PATCH=39