Automatically create PRs that bump the SciPy version.

[brandonwillard]

It would be great if we could create a workflow that bumps the SciPy versions for new releases. Such a workflow could be a cron job that runs at a reasonable interval; executes a simple script to read the latest version numbers for SciPy, check that it's newer, and make the modifications; and creates a PR with the changes using something like create-pull-request.