Incrementing VERSION to 126.0.6478.188

Change-Id: Ia784eff1ceecde3d2e71f30f4665c8a774f4092d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5710488
Bot-Commit: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/6478@{#1785}
Cr-Branched-From: e6143ac-refs/heads/main@{#1300313}

chrome/VERSION

@@ -1,4 +1,4 @@
 MAJOR=126
 MINOR=0
 BUILD=6478
-PATCH=187
+PATCH=188