Auto-bump checksums on last 3 branches (#12934)

We now have all supported release branches (last 3) using the new
checksums format, which means they all work with the auto-bump tooling.

.github/workflows/upgrade-patch-versions-schedule.yml

@@ -20,7 +20,7 @@ jobs:
           query get_release_branches($owner:String!, $name:String!) {
             repository(owner:$owner, name:$name) {
               refs(refPrefix: "refs/heads/",
-                   first: 2, # TODO increment once we have release branch with the new checksums format
+                   first: 3,
                    query: "release-",
                    orderBy: {
                      field: ALPHABETICAL,