Close and open a new PR if a Release PR exists for a smaller version number bump

[pwtyler]

From CONTRIBUTING.MD

if a feature constitutes a minor or major version bump, that version update should be discussed and made as part of approving and merging the feature into main.

Today, if a PR is merged to main with a larger version bump that a previously drafted release (i.e. release-1.2.1 exists and then with a new feature we create release-1.3.0), we would end up with two draft release PRs.

Automation should instead close the previous release as part of creating a new one.

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The most trivial way I can think of way to do this would be to have a release pr tag that is applied adjacent to the existing automation tag. release-pr.sh would close any open PR with that tag with a link to the newly-created one. c/f https://gist.github.com/pwtyler/275e5518cee4882eaf3d529edd3f3bda for prior art creating and then closing PRs, although I think this case will be simpler.