project.config: lock down release-branch.go1.22

This locks down the Go 1.22 release branch to behave like the other
release branches, as per the release process.

Change-Id: Ifd867ac313987dd3e1eb9cd9d7ea987435a6eed5
Reviewed-on: https://go-review.googlesource.com/c/All-Projects/+/560461
Reviewed-by: Cherry Mui <cherryyz@google.com>