dev: improve patch release instruction
Created by: michaellzc
We caught a few problems when @caugustus-sourcegraph walked me through the release process.
In the changeset against the main sourcegraph repo, e.g., #30206, it says update changelog without explicitly explaining how to update it.
Breakdown the manual steps even further to make sure the Release Captain knows they should merge the changeset against the sourcegraph at last. Also, Crystal mentions CI pipeline will always fail before the yarn release:finalize
command is run is confusing people as well.
Fix https://github.com/sourcegraph/sourcegraph/issues/30420 Related https://github.com/sourcegraph/handbook/pull/2114