release `bump` should either automatically update or remind to update README version to `x.y.z+`

[ned-deily]

PEP 101 talks about manually updating the top-level README.rst file to the new version in the final steps (bump) of the release process as part of the post-release commit. In the past, release managers manually updated the version in the README to 3.x.y+ (i.e. 3.12.6+) to match the PY_VERSION string automatically updated in Include/patchlevel.h that is displayed by sys.version and the REPL. That makes it clearer that the repo does not necessarily reflect the state of any particular release - a checkout of the release tag (v3.12.6) provides that - but rather something newer than a release. I think PEP 101 used to explicitly mention this but it certainly would be better to automate if possible.