Incrementing VERSION to 126.0.6478.255

Change-Id: I27dc004ec92491f697bd964d5ba61875c6c2df6c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5893460
Bot-Commit: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/6478@{#1971}
Cr-Branched-From: e6143acc-refs/heads/main@{#1300313}

chrome/VERSION

 MAJOR=126
 MINOR=0
 BUILD=6478
-PATCH=254
+PATCH=255