Incrementing VERSION to 123.0.6312.18

Change-Id: I28aea3825ef4514bb425b3a61bc047ccb4579655
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5328967
Bot-Commit: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/6312@{#220}
Cr-Branched-From: 6711dcd-refs/heads/main@{#1262506}

chrome/VERSION

@@ -1,4 +1,4 @@
 MAJOR=123
 MINOR=0
 BUILD=6312
-PATCH=17
+PATCH=18