Update Python runtime pins (latest patches) and pyenv

[ff137]

Pin each supported Python 3.x version to the latest patch release. (Verified according to latest releases here: https://www.python.org/downloads/)

Bump PYENV_VERSION from v2.6.16 to v2.6.31.

What are you trying to accomplish?

Resolves the problem that Dependabot does not support latest Python versions:

Dependabot does not support your Python version

Dependabot detected the following Python requirement for your project: '>=3.14.4,<3.15.0'.

Currently, the following Python versions are supported in Dependabot: 3.9.*, 3.10.*, 3.11.*, 3.12.*, 3.13.*, 3.14.*.

Anything you want to highlight for special attention from reviewers?

This PR follows the same pattern as #13744, editing the same files, and including a pyenv patch version bump.

How will you know you've accomplished your goal?

All tests pass.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.

[ff137]

urllib3 has a new release (2.7.0) that came out in the last 24 hours.

The Python Poetry smoke scenario now generates poetry.lock pinned to urllib3 2.7.0. And the e2e file in dependabot/smoke-tests (tests/smoke-python-poetry.yaml) still expects the previous lock snippet for 2.6.3, so diff smoke.yaml result.yaml fails even though Dependabot’s behaviour is fine.

So it seems like the smoke test should be updated to account for the new urllib3 version before CI will pass here.

[ff137]

I see there's an open PR in smoke-tests that makes the lockfile change, and so this PR depends on:

• Regenerate pip tests smoke-tests#490