Clarify order of branching operations for SDW component releases

[legoktm]

https://developers.securedrop.org/en/latest/workstation_release_management.html#step-1-create-a-release-candidate-rc-tag says to create the release branch and then push the version bump+changelog commit, but we seem to be doing it the other way, sending a PR for the version bump and then creating a release branch once merged

@rocodes said, "This release process is going slightly differently than previous ones; usually I would do version bump in the repo (client, export, whatever), tag that, and then the version bump+changelog commit in the builder repo would come after that. This has been breaking my brain a little so I'm excited to figure it out."