Incrementing VERSION to 126.0.6478.253

Change-Id: Ic156b0831a50060c7714f234fce53231954a654e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5837841
Bot-Commit: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/6478@{#1951}
Cr-Branched-From: e6143acc-refs/heads/main@{#1300313}