bump posterior version

[jgabry]

closes #752

Submission Checklist

• Run unit tests
• Declare copyright holder and agree to license (see below)

I didn't run the unit tests locally, will let GHA do it for this tiny PR

Summary

Bump posterior version to avoid weird print output

Copyright and Licensing

Please list the copyright holder for the work you are submitting
(this will be you or your assignee, such as a university or company):
Columbia University

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)