update version string to match PEP guidance (#2004)
update version string to match PEP guidance (#2004)

It now matches the regex from https://peps.python.org/pep-0440/#appendix-b-parsing-version-strings-with-regular-expressions
arviz-devs/arviz,arviz-devs/arviz,arviz-devs/arviz,arviz-devs/arviz