Incrementing VERSION to 112.0.5615.121

Change-Id: Idee10048b9c0252103c0611d1ca3e857ad228fa3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4425249
Bot-Commit: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/5615_51@{#8}
Cr-Branched-From: 86d49da-refs/branch-heads/5615@{#938}
Cr-Branched-From: 9c6408e-refs/heads/main@{#1109224}

chrome/VERSION

@@ -1,4 +1,4 @@
 MAJOR=112
 MINOR=0
 BUILD=5615
-PATCH=120
+PATCH=121